Definitely take before pics, and one thing I would suggest... take creatine daily. Not only does it make your gains look more impressive, but it aids in energy output and (as I found out recently) its been shown to be beneficial for anxiety and depression too.
Flat green screen personally. I don't mind if background obscures gameplay if it can't be helped (ie if someone doesn't have a green screen) but having one and superimposing a background (and obscuring gameplay) would probably bother me.
oh good lord..