nice take on the challenge, colors and composition are good, lighting is well done, the only flaws I see are the upper left & right corners are a bit distracting
I very much like this image. Particularly since it evokes rest to me, as most guitarists' hands are very busy with their craft. Only suggestion I can think of is a slightly tighter crop so the bits of color in the corners were gone (keeping the background black with the hands and guitar standing out), but really that's being picky probably. Nice strong image!
I thought about doing something like this (but my instrument's bass), but didn't know if I could pull it off. Nice job. I like the soft light and the warm colors. A tip: I notice the jagged lines in the strings, which usually comes from resizing. Try resizing in steps (say 20% at a time) - it usually minimizes, if not eliminates this.