This cycle's themes have been determined. I generated two lists, one based on technical concepts like the level or type of PC, and the other based on more story oriented ideas. Most of these latter were derived from the unused ideas from the original challenge (found here, but I addded in several more derived from Magical Master's list earlier in this thread (#16-18), and several more I thought up myself (#19-21).
1st List ("technical") - note levels should be considered approximate (e.g., if one got "Level 10 PC", one could make a module for Level 10, or Lvl. 9, or 11, or a scaleable module for Lvls. 8-12, etc.):
Make a module for a...
1) Warrior PC (meaning primarily the classes with full BAB progression, fighters, barbarians, weapon masters, Dwarven Defenders, etc.).
2) Level 5 PC
3) Healer PC (primarily Cleric or Druid, but Bard or Paladin might work too)
4) Level 10 PC
5) Arcane Caster PC
6) Level 15 PC
7) Thief PC (one requiring stealth or other roguish skills, probably but not necessarily an actual rogue)
Level 20 PC
9) Druid or Ranger PC, or at least a wilderness themed adventure suitable for such classes
10) Level 25 PC
11) Shapechanger (probably a Shifter, but a caster with access to polymorph spells might work too)
12) Level 30 PC
13) Assassin (meaning a PC whose primary occupation is terminating high-value targets, not necessarily limited only to PCs who are Assassins in the sense of having taken levels in that class)
14) Level 35 PC
15) Bounty Hunter (I already did this, but I hardly exhausted the possibilities for this type of character)
16) Level 40 PC
17) PC who is a member of an order or organization with a distinctive code or ideology (I thought this up with monks or paladins in mind, but other class possibilities exist)
...or make a module with
18) no haks or other CC
19) only one hak
20) a Time Limit - must complete the adventure before time runs out.
2nd List ("story"):
1) Weather or Not - Weather plays a pivotal role in the adventure
2) Disastrously Yours - Similar to the above, a disaster, natural or otherwise, plays a pivotal role in the adventure
3) A2B - A simple journey from point A to point B. What could go wrong? A lot, actually.
4) Trading Places - an adventure set in some alternate mirror universe, for example one where evil has triumphed and lives in the over-dark while the remnants of good huddle in the under-light.
5) Stop Frodo - Either the PC or an NPC has been charged with taking some artifact to the one place where it can be destroyed. Unfortuantely this quest was assigned by someone who was actually an agent of Evil, and this artifact is actually necessary to prevent said Evil from triumphing. The bearer of the artifact must somehow be stopped without being killed.
6) A Plague on You - The PC is tasked with the seemingly simple task of eliminating a plague of vermin, but in the process stumbles on a much greater plot.
7) Meddling Kids - The PC comes across a town where all sorts of strange things are happening, and a group of teenagers and a talking dog are the only people with a clue as to the cause (more generally, a Scooby Doo inspired adventure, even if one that does not correspond to it that exactly).
Time Travel - Time travel is involved in the adventure in some way
9) Shakespearean - an adventure based on a Shakespeare play in some way
10) Inheritance - the PC has just inherited something that leads to adventure: could be an item, a tract of land, a title, a family curse, etc.
11) Save the Princess - A rescue mission. From Tristram to Dudley Doright, heroes for centuries have been tasked with getting the girl. (Note: if desired, object of rescue can be someone other than a literal princess, e.g. a prince).
12) Storm the Castle - Some villain's citadel needs to be assaulted
13) Fairy Godmother - the PC is assigned a dangerous but heroic task by an NPC who also provides some magical aid in its accomplishment.
14) Escape - the PC finds himself held captive, and perhaps stripped of his gear, by hostile forces, and must somehow escape.
15) Everybody Out - everyone's minions/henchmen/whatever have gone on strike, and it is not clear why. The local adventurers' guild/thieves' guild/whatever is offering a reward to whoever can resolve the matter.
16) Amnesia - the PC begins the adventure not knowing who he is or how he ended up in the circumstances in which he finds himself. Naturally answers to these questions, and the question of how he came to forget them, must be found.
17) Siege - an adventure set in a city under siege (or maybe in the besieger's camp).
18) Mysterious Artifact - An artifact has been discovered, and its purpose or some secret concerning it must be sought out.
19) Double Agent - the PC is tasked with infiltrating some nefarious group so as to undermine it from within. This could, but need not, involve a Shifter who can assume the form of kobolds, drow, dragons, or other monsters.
20) CCC Tie in - Pick one of the themes used for the monthly Custom Content Challenge, and make a module based on the same theme.
21) Blast from the Past - Pick a theme chosen for a previous cycle of the Adventure Building Challenge to be used again. For this cycle that would mean picking one of these themes from the March 2013 ABC:
A) Treasure Map - the PC has come into possession of a map said to lead to treasure...
Into the Abyss - the PC finds himself on a journey through fiend-infested planes.
C) The Real Anti-Hero - the PC takes on the role of the goblins PCs routinely slaughter (or something along this general theme where the PC is the champion of the "Bad guys").
...or one of these from the April 2013 ABC:
D) Pieces of Eight/All at Sea - a watery adventure set amidst an archipelago of small islands, possibly but not necessarily involving pirates.
E) Perilous Lodgings - the PC takes refuge in an inn, house, etc. that proves to be much less safe than anticipated.
F) Summoned - Inspired by the Summon Spell. Instead of a dire animal, elemental or planar beastie, some powerful magic wielder ends ups summoning the PC, intentionally or otherwise, to aid him.
The plan is to pick two themes from each list, which participants can mix and match as desired. For this cycle, I determined that #21 from List 2 ("Blast from the Past"), would automatically be included, so that anyone who was thinking about doing something based on one of those themes in the original ABC, but did not get a chance to complete it, would be given a second chance to do so. The other 3 themes I determined randomly with 3 d20 rolls (so those results were as much a surprise to me as they are to you). That gave us:
1) Module for a Warrior PC and
19) Module using only one hak
from the first list and
6) A Plague on You
from the second list. (Plus Blast from the Past which gives a choice of 6 possible themes). Participants are expected to employ one of the four themes and are encouraged to combine as many as possible (e.g, make a module for Warriors, or a module based on the "Plague" theme, or a module for Warriors, based on the "Plague" theme, that uses only one hak, etc.).
No doubt both the lists and method of selection from them could use considerable refinement, but this should be good enough to get things started.
As for allowable CC, I intend to keep things simple by just using the original sponsors, with the addition that one is permitted to use a hak from any Custom Content Challenge Cycle, not just those listed on that page. As I said earlier, it might be good at some point to look into generating a more up-to-date list of sponsors, but I am not sure we can both do that and get this off the ground in a timely manner.
I think I will have participants make their own module entries, rather than there being a single consolidated one as the only opinions expressed one way or the other favored that. I still think there are some advantages to the "single entry" method, so perhaps that could be reconsidered for future challenges.
More info about this ABC cycle coming soon. Stay tuned.