hmm. I'm not sure I can tell you how to do it right, I'm having some trouble mountains myself (though yesterday i think i had a breakthrough) but one or two things:
the snow areas come over as flat. like plateaus with snow and ice rather than very tall peaks.
what I found yesterday was that when I tried to draw the mountains with just one ridge they didn't really 'fill out' the area thats supposed to be mountains (I'm doing a world sized map too). then almost by accident I drew several ridges overlapping and merging which in my opnion gave a very realistic look. try zooming in on the Alps or Rocky Mountains in google earth and it might give you an idea. even though mountains are depicted as one big ridge there's often more to them than that.
I'll post my WIP in a few days and you can see what I mean and return your opinion
Oh and don't forget the parallel ridge in the upper left 'square' of the Mordor area. It's called the Morgai.