Another thing that attracts players is by having something that you can put a stamp on, to say is yours and no other server has.
For a while I was very much into creating Cutscenes using the Gestalt Cutscene system for my PW, and by using nwnx_areas - to keep them modular and player focused, I was able to create a cinematic experience for players.
Also consider the resources your module has access to.
I used a Downloader application to give players access to optional material.
Eg: Sound Effects, Audio voice overs etc for cutscenes etc
These sorts of thing can really make a player go 'wow' because it shows that you put the effort in.
I had a few people telling me they used to run some of the quests just to see the cutscenes, cause I mostly had them scripted perfectly with the music.
Besides cutscenes and hak pack content etc,
maybe consider the end-game content.
For the first half of my servers life-span, players fell in love with my Vampire bloodline system.
It was basically a clan system that allowed all players to accumulate bloodpoints from a portion of their XP gains.
Those bloodpoints could then be used to buy bonuses for your vampire.
If you had sired other vampires (players) - then they would be in your clan, and inherit your bonuses.
If they sired anyone, they too would be in your clan etc and so on. (but they could not spend bloodpoints, only the clan leader could)
(Imagine a pyramid scheme where everyone receives equal reward)
Eventually, the system became overpowered - So I had to nerf it, but it attracted alot of players who just wanted to be vampires.
One of my quest lines involves a Shadow Monster that clones the player.
Because the player in this case was a vampire, with such high AC, and that AC had been copied to the clone - it ended up being a perma stalemate.
Neither the evil clone or the player could hit eachother.
Players are often attracted for systems that allow for customization.
One System I made was the 'Forge of Olonwi' (was actually a parody of a Friends character they made on my server)
Rare loot drops 'Star Sapphires' - could be used as currency on this forge system.
What it did was this:
In one receptical - you put a trash item with good properties on it.
In another receptical - you put the item you wish to enhance.
In the payment slot, you put 1 or more star sapphires.
When you trigger it, it will destroy the first item : Taking one of its item properties, chosen semi-at-random,
and copy the property to the item you are enhancing.
First generation of this system made items well overpowered, but I managed to balance it by changing the item property copy settings,
so it would not stack item properties of same type.
Eg:
You could not end up with
DamageBonus 2d12 Negative
DamageBonus 2d12 Divine
DamageBonus 2d12 Fire
and so on
What you could do however was get 3 Damage types, but using the 3 different Damage Bonus item property types.
Eg:
Damage Bonus 2d12 Negative
Damage Bonus 2d12 Fire vs Evil
Damage Bonus 2d12 Divine vs Undead
This way, the system was balanced and players had to be strategic about how they use the forge.
Eg: To get the 'correct' item property, they might have to transfer the property several times, to junk items, until they have just one property for the system to choose from.
Another thing to think of, which is somewhat easy to do,
allow players ability to change
Portrait,
Head appearance
Voice Sets (if permissible by the module theme)
Players hate having to re-make characters, just because they can't get the voice set they want, or head appearance that is sexy enough.
Allow them to do it all from in-game, and these quality of life improvements will pay off.
Other things - Such as Server Vault management etc
Provide some means for them to clean out their old characters from time to time.
Eg: Letoscript deletion or renaming of character bic files so they don't clog up server vaults.
Anyway - just alot of ideas there