Critique Please?

Hey, my name's Vyper.

Just wanted some critiques on a digital painting I did.

http://vyperion.deviantart.com/art/Plants-4-Zombies-486450910

Although you're free to critique whatever you want, I am mainly looking for critiques on:
1. Composition
2. Lighting
3. Colors
You don't need to tell me I can't draw folds. I already knew that. Haha.

Hello, Vyper, and welcome to Line of Action. My name is Polyvios, and how are you doing tonight? Say, I don't see your dead link from DeviantArt yet. Please reboot it now. Thank you.