I think it looks pretty good personnaly. You might find that it might not last to long just being painted on though because paint might not penetrate the leather very deep. If your feeling really brave next time buy some leather dye and use that because it will penetrate the leather lots more than the paint but it is a lot more difficult to work with. Also you can just touch up the paint from time to time as well!
Like I said looks really nice and I like the contrast.
Sealing should definetly help it last lots longer than if you don't. Looks good and I wish I could do something like that when I get bored! I have to get my self amped up in order to draw patterns because it takes me so long.