Not bad. Adding a border would be good. If you're using photoshop, create a blank layer on top of all the others, hit Ctrl + A to select all and go to to Edit: Stroke. Also, to help smooth out the lines around the figures, add an outer glow. Some people are really against this but it helps eliminate choppiness and I think it brings a peace together nicely. It also helps things stand out off a background. Just screwing around and experimenting with the features can be good practice, as well as researching tutorials on the internet.