This was a quick image I made in the Gimp (30 min). Second thing I tried with my new Intuos4, so I know, it is not that good, but it was quite a bit of fun to make.
The drawing itself is cool, but there is way to much black area around it. you should crop it down a bit and maybe add some moonlight shining on the hand so we can see a bit better, It took me a few seconds to find the hand in the dark area and with the lack of light.
Hmm… On my monitor, it looks quite bright… Although I am sure it would look darker on the other ones that I have… Or is it possible that you didn’t click on the image to expand the size?
I see the hand on my tapbletpc only with brightness pumped up! So I think that there it is a problem of contrast amd that you must use more vivid colors.
Is this a bit better?
Added the original sketch
Try to use gray shades for the start. The sketch looks nice.