For me, I haven't really had the time or the spark of a good idea yet. As elephantinc said, this one is relatively specific, so I'm finding it hard to get a good concept going. Also, I'm not very comfortable with character modelling yet, especially realistic humans, so I'm not as quick to jump into it.
It seems to me that most of the challenges recently have been of the model something and texture it type. This is a huge area, but Maya also has a lot of other areas that might be fun to explore more. I know animation is optionally included in the challenges, but what about a dedicated animation challenge where everyone is provided with the same model or something. (That would be more work for someone in setup, but I'm sure someone has a rigged model around). Or, some more ideas:
-Make your best dynamics simulation of everyday life: e.g. putting out a fire, pouring some coffee, a thunderstorm
-Produce a wallpaper-type image involving abstract objects and interesting lighting and rendering... e.g. caustics, reflections, chrome spirals... whatever
-Make some sort of crowd animation... e.g ants marching, people on an escalator, soldiers approaching battle (this challenge would probably be pretty technical, maybe too hard)
-Make an animation personifying an inanimate object... e.g. a talking chair, a depressed airplane, an angry lamp
-Make a 3-5 min tutorial explaining a cool Maya feature and showing it off by creating a little scene that exploits it (ok, that one's maybe too different)
Just thought it would be good to steer away from character modelling every so often... maybe the trouble is that it's been two in a row of a relatively similar challenge.
EDIT: Oh yeah, and the lack of prizes isn't a deciding factor for me either