I as well think it'll look good and provide a good contrast. I mainly just wanted to do something outside of a stock grey keyboard.
My little brother has been using spray-on Plasti-Dip on EVERYTHING... he painted the VW badges on his Jetta black, his rims black, his motorcycle helmet green, and who knows what else. If this stuff can stand up to a Wisconsin winter and salt on the roads after he sprayed 8 coats on his rims, I think it'll do damn good on a keyboard frame. Personally, this will be the first time I use the stuff. At least I have an expert as a sibling.