I think you've done a fantastic job overall, but after looking at my own hand I decided to do an edit.
1. Are your fingertips really that narrow? Mine are considerably wider (and some images I've seen) so my edit reflects this.
2. Fingers taper as they lead to the tip, while yours don't seem to do so as much as they should.
3. The pad at the top of the palm wasn't visible and made the hand look awkward so I added one.
4. Mirroring that hand pose I was unable to see nearly as much of my thumbnail as in yours, so I think the thumb perspective is slightly off.
5. The right side of the palm protrudes beyond the pinky and makes a gradual curve back to the wrist. .
6. Added slight shading based on an overhead lightsource (how the shadows fell on my hand).
this shows the changes more clearly.
Hopefully some of this will be useful. Again, your hand might really look this way so some of these edits could be ignored.