You said earlier in your posts that you were unable to draw. I understand this b/c at one time Hands were too difficult for me to draw
My problem was that I concentrated too much on drawing just the shape of the hand. your case is slightly different because you are using a program. But! I would say that you need to add expression in the curves of your hand... (HEY Where's Jango when you need him?) Also remember, the hand is a pulling, pushing, grabbing, twisting mechanism. It has padding to achieve this. I see you've added these on the palm, but there's more padding right on the top of the palm ...which is partly why your fingers appear flat on the palm side. Also the hand inclines down... er... by this I mean that the base of the palm should be stick out alittle more- but after the palm the bottom of the wrist(the side with the tendons visible) should be made more inward as an effect of the wrist being able to push an object.