Very nice, especially for your first attempt at this kind of map.
Couple of things that seemed 'off' to me (and these are just my opinions, do with them as you will).
- Mountain tops seem awfully bright white - are they largely snow covered? If so then ignore this otherwise you might want tone it down a bit.
- Continental Shelf - Drop off seems kind of abrupt to me. I think I might soften it a bit - again if you intended it to be that drastic then by all means don't change it.