That's a great idea!
I can't tell you how many thousands (ok, maybe a bit less) of blogs, websites, and forum posts I had to dig through while looking at other's CP's to get ideas/inspiration/tips.
(angle joysticks on 4p or not, distance to screen for trackball, how many/layout of buttons, etc..)
It would be nice to have one spot for people to share their designs so other's can learn and get inspiration!