Clean the lines and avoid jaggies.

There are too much grass titles, looks like your character is stuck between them, give him more space to move.
That sphere is a monster ? add some arms/legs/eyes/tails/horns... and maybe an hp bar.

Dithering on the mountains can be a nice thing.

 Here's my quick edit http://img32.imageshack.us/img32/9925/rpg53255.png

Dennis is right, and i suggest to simplify the characters even more.

http://img15.imageshack.us/img15/2922/rsgh4waffa.png
light siluette

Thank you.

Wow thanks, now it's much more better and i thought that leaving the trunk simple would capture the attention on the foliage, well, silly me.

@Mrmo Tarius
Naa, they are just "tetris blocks".

@Delicious
My first SERIUS attempt AFTER reading/studing a bunch of tutorial and stuff.