OK.. good start as a I noted earlier. My first suggestion is lower the opacity on the texture as it is a bit regular and overwhelming, but that's just me so not a big deal.
Most importantly are the trees. While they look ok individually, they are a bit sloppily laid down in places and it detracts from the whole. Of course, if the idea is to do this super quick, then ignore that.. I would also suggest adding a bit of shading to the trees themselves(not in the tutorial) to give the impression of depth. In this case, a bit darker on the right(or more bottom right) and a bit lighter on the left/top left. It takes more work and time for each one, but really makes them "pop".
Mountains look good, but I would shy away from using the white for hightlights as it is to big a contrast IMO. go with a lighter shade of brown OR if you put a more cream color on a separate layer and blur it a bit and then clean up any over runs, that should work well. A bit of blur would be good in either case... You might also consider increasing the size of the mountains by about 50-100% either in the original images OR preferably as you paint using the scale on the brush. As it is now, they are quite close in size to the trees themselves.