It would be awesome if you added a Dark Steel Door that could be painted much in the same way as the existing Dark Steel Trapdoor.

Suggestions are now being tracked on:
http://ideas.theideawall.com/EnderIO/

Please post your suggestion there.

EDIT: actually, a Dark Steel Door has already been suggested on there. I suggest voting for it if you want it implemented.

Thanks for the hint, I just saw that it was already suggested :D