as far as a challenge that would actually get my attention...
so many people want to focus on so many different things, obviously according to their own talent (and experience) level... as for me, i can create nurbs objects and create textures for them to make them seem somewhat realistic. i've seen people that can model actual (existing) objects in polys, sub-d, or nurbs and then render them to make them look good. i've seen people model half-assed things and render them in plug-ins or other renderers and make them look amazing no matter how the original model looks or was created.
i believe that focusing on a certain object is key. creating textures, bump maps, lighting, particles, etc. should all be done with knowledge of base maya. no mental ray, no 3rd party renderers, no z-brush. use maya. use maya's built-in materials. use maya's built-in modeling techniques. use maya's built-in texturing, lighting, and software rendering.
i understand that there are others from other 'simply' forums that want to compete because their forums are dead... i believe there's a reason that our forum is flourishing as well as it is currently... it's not because of zbrush, it's not because of modo, it's not because of (enter alternate 3D package here)... simply maya has done well because of the support of users of maya.
therefore, i suggest that maya should be the program all 3D aspects are conducted in. obviously, 2D (such as texturing) is up to the user/entrant.
i offer that if there is to be a challenge, let it focus on an aspect that members can learn from... but let it be a focused aspect. give us a lighting challenge. give us a texturing challenge. give us a rendering challenge... but only allow us to use maya. no plug-ins. no third party renderers. no 3d painters. after deciding which challenge you decide to give, you can THEN decide the rules. allow us photoshop, or not. allow us maxwell, or not. allow us zbrush, or not. allow us mental ray or renderman, or not. the more specific you make a challenge, the more it actually CHALLENGES us to learn more about the program, and the more it increases our skills.
Accept no substitutions.