This is something that I struggle with in my vision of the perfect day.
Steampunk generally encompasses a range of browns, copper, brass, golds or blacks. I really prefer the browns, but at the same time REALLY like jewel tones and bright colors. Part of me thinks that browns, lavender, pink, and a green would be most reflective of a Steampunk wedding. But here are some sites that are really helpful.
The Multicolr Search Lab by Idee searches Creative Commons photos and puts together a photo collage based on your selected color palette. Careful, though, it is rather addictive.
The website here: Idee
Have fun! Here are some of my ideas.
I KEEP GRAVITATING TOWARDS THIS COLOR RANGE!
My boy likes this one: