Well a revolver is not exactly a black-powder type weapon. It requires the invention of percussion caps, which are a fairly modern thing.
I guess if your steampunk character actually made a black-powder revolver, and somehow made it work with a matchlock or flintlock mechanism, (or other) that would be interesting and exotic enough. I don't think you could get away with just saying "oh, these things just exist."
Percussion caps are not all that modern. They were first invented in 1805-07 They were used almost exclusively during the civil war for black powder weapons, including a wide range of revolvers. The colt walker, the navy colt, remington rider etc.
Granted, loading a black powder percussion cap revolver is a pain in the rear. You have to cram the powder down into the chamber with the ball/bullet on top using a lever thingy (this is my awesome girl terminology kicking in). I'm pretty wussy and can't get it to pack down. Heck, I can't even open a pickle jar. Not something you'd do in the middle of a fight. Most cavalry men kept spare loaded cylinders on themselves so they could switch them out during a battle.
I guess that could be a limitation as well. A gun like a derringer only has one shot and then has a lengthy reload time before it can be used again, which would make a backup melee weapon handy in close quarters.
ETA: Just a note, if you use percussion caps as primers, crimping them with your fingers before putting them on the nipple will prevent them from falling off while being wildly waved around. Otherwise you're kind of screwed.