Here's a fun little abstract tree I did for my friend, Becky's nursery yesterday. I know, I know, leaves don't come blue & green! But hey, we wanted to bring in some of the colors of the crib bedding, so they're intentionally blue! And I DID say it was abstract. It turned out really cute & looks great with the decor! 
This was VERY easy! If you can color in the lines, you can do this!
1. Draw the basic shape of your tree lightly with a pencil. Don't be afraid to draw on the walls! I have to warn you, though, you may have to talk to your kids about it if they catch YOU doing it! My kids have colored plenty of walls in my house... but how can I be upset if they see me doing the same thing?! No biggy, a moist Magic Eraser (Mr. Clean) will erase any mistakes. **Notice there's a shelf on the wall. Just draw & paint your tree as if it weren't there. It looks fine.
2. Draw, then start painting your leaves. I used 6 or 7 different shades of green. It looks best if you do one color at a time, spacing them out a little.
3. Using the rest of your greens, finish the leaves. Fill out your tree as full as you'd like! You could also paint flower blossoms instead of the leaves... or just leave it bare!
4. Add the blue inner part of the leaves. I used 3 shades of blue. I started with the darkest blue on the darkest leaves, then tinted the blue paint a couple times with white to lighten it & do the lighter leaves.
This is a picture of a tree I did for my friend, Brandy's nursery. Hers was a more organic, flowing shape. To make it look more natural, once the tree & leaves were painted, I added highlights & shadows. If you choose to do this, make sure they're consistent. I mean, make sure your pretend sun is highlighting the leaves & trunk in the places it should be.
