I think i've finally put my finger on what seems off with the mountains (at least to me). It's the dark shading. the darkened portion (left mountainside) is too uniform, there's nothing that really breaks it up.
It might be because I've gotten used to hand drawing them with lines, there's breakup in the pattern that way. In these, the shadow areas are solid.

Not really sure how to change that without doing a lot of work. perhaps a layer style with a pattern overlay of a broken up set of lines..