Many of you know CGTalk Lighting Challenges
Every challenge start with a 3D Scene and the goal is to "light" that scene the best way
The good thing is that all the scenes used in previous challenges are available online
You can go to 3dRender website and check the Lighting challenge section
There's 21 scenes modeled by various talented artists that you can download
Every scene is available in various 3D file formats (included wavefront OBJ)
There's a gallery for every scene, because every scene is a past challenge where tons of good artists have worked
This is perfect both for inspiration, and for experimentation
Notice that its free only for personal usage with appropriate credits (to the modeler)