The restrictions are mostly there to make it so most players will be able to complete it in a reasonable time, and to not make it a scripting nightmare by including elements that would take a long time to script. As long as it doesn't break this I'm willing to discuss any ideas you have. I would not be opposed to having a party requirement like someone mentioned for example, but not with too many people or specific classes required, since people might have problems getting a party together then.
If you have any specific ideas you want to ask about and don't want to share with everyone feel free to PM me on here on the forums.
You will not be able to name NPCs after players since, as Silk says, thats a donation privilege.
As for sprites, here is a list you can pick from: http://www.dotalux.com/ro/npclist/
I ask that you don't pick ones that are used for well-known custom purposes however, like Pandolina for example.
