I don't really have an idea yet haha, but dark and gritty sounds pretty damn perfect to me. As you may remember I like a really strong colour and picture theme between my Avatar and Signature, so if we go for blacks, greys and gritty bronze colours? does that sound quite cool? with one or two bright highlights in places? 

Do you want me to find some pictures?

EDIT: on one hand I've always wanted a set that looks like those old Russian propaganda posters? with the really strong symbols of the fist and hammer etc. 

http://2.bp.blogspot.com/-293AiYg8Ovc/UG7pK-G96DI/AAAAAAAAAFE/AItucG-eNTg/s1600/1294745242v3igD2.jpg

but with some more original twists, to make it more modern. But I can definitely leave that idea as it's not my only one.

Steampunk is a nice theme, lots of gears and steam and sparks with a cool aged look.

There was one other idea which I put to someone else but never seemed to go anywhere, but it's kind of a complicated one I think, wouldn't be so dark & gritty unfortunately so I'll leave that one for now.