perhaps its time to change the challenge forum to something a bit more collaborative. After all the industry is all about collaboration.

Solo challenges probably put people off if they are crap...

check it
http://simplymaya.com/forum/showthread.php?t=38287

hey! yeah my challenge idea, a last hurrah!

cool so...
Its like i said before, get a assigned a random number page and use any or all of the models available. you can modify the model or...

i still think a lighting challenge would be the funnest.

Each person gets a random page number and has to compile a scene using any or all of the models on the page. shading and lighting. ...

Haha, well I didn't think you would be entering :P

Architecture is a great idea.

I would say if someone has to drop out, its no big deal getting someone else to join the team to pick up the work.

yeah cool :)
perhaps you don't need someone with a speciality, and in fact a generalist role would be more useful i guess.
this could work for someone who wants to learn more animation but maybe...

i've probably suggested this before, but what about a group challenge?
one modeller, texture artist, rigger, lighter, animator
two or three teams maybe making a full cg environment and...

how is rigging and animation hard to judge? rigging alone perhaps, but you can have crap rigs and good rigs, and more complicated rigs with good skinning just like you can have crap models and such....