Personally, i think it looks very white-washed, but i think you've gotten that impression from all the people commenting on the desaturation.

Here are my suggestions:
1.) use a color other than green for the shadows (of the trees), maybe purple.
2.) the top (3) water tiles. put dirt between where the waterline is and the grass starts (to give the allusion that the water is lower than the other tiles, like you did with the ledges), so it doesn't look like a puddle.
3.) use a different color for the menu. all the muted greens make it really mono-tone. (you want the game to POP. )
4.) on the tiles where the grass meets the dirt, add a darker green on the *bottom* of the little wisps of grass to give it depth (make it look like the grass is actually on top of the dirt)
5.) again on the grass-metting-the-dirt tile, clean up the dithering job, remove the single pixels of green on the dirt, make the little 'spikes' of grass shorter, grass blades aren't that long.

It's looking really good, i think the finished product will be really great, it's come a long way.