The colours are good too, although i'd say try cool colours with this extraction due to his silver clothing.
I see you didnt put any text in, It does loook difficult to place it in this signature, but if you just experiment around with text you can usually find a good placement. Try different colours, different placements, different layouts or even try putting text in the background (especially in signatures that are mostly empty this seems to work well).
Anyway this signature is awesome. C: