Green troll against a green background... not a good idea! ^^'
I would suggest to change the picture for another one with a more neutral colour or even white, you can also print out something and use it as a background! ;)
On the miniature itself, If you paint the "scales" with a different colour it might look quite a lot better and even won you a bit higher votes, for example, you could try painting gray scales, or maybe dark brown, or if you go the bold way even purple or orange! Look on google and get a little bit more inspiration, but overall, have fun!
Oh! I was forgetting, the grassy back idea is interesting! You can even add a couple of mushrooms there ;)