If you really only want it for squirrels or other critters about that size, I'll throw my hat into the .32 caliber ring. I've had or have .32, .36, & .40...the latter two can work great with head shots only, but any body shot with those can be pretty severe. First squirrel I shot with my .36 and 30 gr of 3F literally came down in pieces. My .32 with only 15 or 20 gr of 3f was more like a .22 longrifle. Still more potent and required careful shots, but at least I felt OK with ribcage shots with the .32. Just my experience. Others may vary.
I'm not sure what you're asking in reference to silver inlays and wire...do you mean historical pictures of squirrel rifles so adorned? Pictures of reproduction guns so adorned to get ideas?