The color on your early wip looks like its a refelection on the ground. Alot going on the picture witch is fun to look at.
Initially I painted shadows, but refused to use them.
Early WIP
I love it. Even the garish colors.
Maybe some ground shadows will give the BG some flair so its not so plain as Mandrill mentions.
A real cool piece but that plain and flat backround kills it for me. 
the ground hurts my eyes slightly but other than that its a nice style
his is an really cool piece