Signatures a little old lol and I've thought about a sculpin, just not sure where to find one in Colorado.There are a lot of cool fish you could keep in a ten gallon. If I had an empty ten I`d look at a wasp goby and a butterfly catfish. I think both stay small enough to do well in a ten gallon.
I see on your signature you have some native species. If want another native a sculpin would be a good fit and they are a blast to have.