Album cover - The Sensational Robot Band!

I bought some new charcoal pencils the other day, and used them for this sketch. These guys seem like they'd be a blast to go see in your local club! A little different style for me, so suggestions/comments are as always totally appreciated. Original sketch is here. (Honestly i think i kinda like the original sketch better before adding color.)

(Doh! the square image cuts off, so click through to see it fully)