Great Start! Hands are especially difficult to make right.
Just a few pointers:
The scene is kind of dark, try adding a fill light 90 degs off from your key ( see 3 point lighting ) This would make your scene more visible so that you can see more detail on the hand.
Your cutting of the model for UV mapping it totally fine, but check out projection painting/cloning to make the texture transition seamlessly (MaxMcdragonturd 's Texturing in Blender 3d (Clone Painting) is a pretty good tutorial )
As for the model, try bending the fingers a little bit. Rarely do you see pictures of hands where the fingers are stiff and straight out.
the left side of the palm bothers me. I think you need another loop or something to distinguish the hand topology from the wrist topology.
Starting with something like this:
And then add a loop to set off the wrist so that it doesn’t look so stretched
Best of Luck