We are indeed getting a new site, and the simply maya community will have a lot more space than it does on the current one so we'll have a good chance of making more of things like these challenges.
I agree that scene breakdowns are very useful and interesting to read, we will have some new forum categories and one will be on articles for featured work and what went into making it. Adding good final challenge entries to that is a great idea.
For a texturing challenge it does go hand in hand with lighting, what I was thinking if we did simpler scenes was that we could have monthly themes sometimes to focus on specifics for example it would only be allowed to use geometry based light sources and no indirect illumination techniques, or shade a full scene using only procedural textures, or make every shader based on the architectural material, or texture painting for skin on a premade character provided and so on. And we could add a sticky or create a free tutorial with some basic information to get you started and encourage more people to join. So I'm with you on that one Ben, as well I think getting restrictions can be quite useful sometimes not to get lost with too many ideas.
Another thing we could do sometimes would be to make the general challenge a clean modeling challenge where you'd have to finish on an ao render, for example it could be modeling an interior or a cartoon character and then we could use the winning scene (providing the winner was up for it of course) in a lighting and shading challenge after that. I think that would make it easier for a lot of people to enter a challenge as well, because I know I wouldn't enter a challenge that required modeling, shading and lighting a character because modeling takes me ages and I would run out of time to complete it. Also as there's a lot more people who model on this forum it would be a nice way of learning by seeing what someone else could do with a scene that you modeled.