I am programming an isometric rpg using C and Carbon. Up until now I have been storing all of my npc sprites together on one single 'npc gworld'. For the sake of creating a more clean and somewhat data-driven design, I would like for each npc sprite (that is each different type) to have its own gworld. Now I know it will be about the same amount of space, but I just wanted to know if anyone here can think of any downfalls for this? Is there any reason at all (technicaly) that I should rethink doing this? Thanks alot.

There's nothing wrong with having multiple GWorlds. As you say, it'll allow for a more data driven (or object-oriented, if you like) design, and there's no appreciable downside. Go for it!