The photo is great but I noticed something. Where the cut is, you can see the lines that are kinda like fingerprints that are on your palm. Maybe you could try blend those in. It's already really really amazing but I just thought I'd point that out for ya.
I can see your point, but leaving the prints there gives a texture similar to that of muscle and sinew, rather than just having a smooth surface.. which isn't very realistic. If this were a prosthetic I would have sculpted in the muscle instead.