Here are some ideas for the next texturing competition:
Doodad pack - take one of those textures that apply to lots of doodads and make a fitting doodad pack out of it.
Original Species - convert a Warcraft unit into an entirely new race or creature that you have created yourself and that doesn't exist in any story, game, movie, etc.
Total Conversion - texture a warcraft unit in such a way that it resembles the original as little as possible. Preferably have the head in another place than it was on the original model, change the legs into something else, etc.
Race Conversion - The same theme as texturing competition #2, take a warcraft model and texture it to fit either the alliance, horde, scourge or sentinels. I think this is till fun and interesting and should provide useful skins for mappers.
Creeps - Same as above, but you have to convert something into a unit of one of the creep races, like ogres, centaurs, etc.
Animals - Convert a warcraft unit into a real world-animal. Could include anthropomorhpic characters as well.