Adding these to my list of possible themes:
Ruinous Intent: Not necessarily just ruined buildings. Could include such things as ruined pictures (or even pictures of ruins), shattered statues, despoiled books and scrolls with missing passages, tornado blasted trees, etc.
{ Suggested by: Tarot Redhand }
Blast from the Past: Make a single new thing that fits a past Custom Content Challenge theme.
{ Suggested by: Carcerian }
Post Apocalyptic: Not necessarily a modern/futuristic content, might include various mutants, demons, animals, undead, especially zombies/ghouls, radioactivity or weird magic effect scripting support, ghoul/zombie/skeleton raising scripts/animations, wastelands tileset, dead trees, various twisted vegetation, various masks/goggles/other protection.
{ Suggested by: Shadooow }
Something Familiar: Additions or modifications to NWN familiars. All-new familiar creatures, new behaviors, new spells that affect familiars, special items that affect familiars right when they are summoned, familiar-related quests. etc.
{ Suggested by: Shadowing2029 }