There's a few redundant shades in there (I count 13 colors, you could probably take it down to ten or less). Also, I think because of the peculiarly shaped highlights and the slight pinkness, they seem more like flower petals to me than rocks.
You seem to have a little problem with tiling there: you are making 24*22 tiles (which is quite odd) and putting them on a 23*21 grid.this is a small edit showing you how to define the shapes of the stones a bit more. its a very tricky thing to do and you have to be carefull at selecting each shade for the different pixels. actually my try at it isnt perfect either but i hope you can learn something from it
It would benefit you a lot if you sketched in most of the elements on the level early on. This way it's easier to judge what kind of detail goes where. If you do an ubercool superdetailed rock pattern now, it might look too hard on the backround or sprites. Keeping everything under control is more important than a cool rock pattern.Also taking a walk through the forest will be far better than a tutorial on the web i thinks
Anything will do really as long as you have an overall battleplan. Just put in some colors without going into pixel detail right away to get a good mood going on in the level. Try not to get stuck into things. Sketch loose and fast. Like this you might end up finding something funky inside the mess. If it's hard to springboard the inspiration from what you currently have, think of something random, like bunnyhoodman in happyforest. Carrots to collect and so forth.... or whatever
