That being said, I think the forest background could look very good in-game (as long as the trees aren't smiling at you). I think it looks better than the one we currently have, IMHO.
A quick bit of constructive criticism: Instead of trying to redraw the game in your own graphic style, as brmbrmcar pointed out, try to draw some graphics that fit into the current supertux style. Take a look at https://github.com/SuperTux/supertux/projects/3
and see if you could contribute to any of these. The Supertux team always needs more artists, and especially so with the upcoming release of a stable Forest World.