It's really cool! I like the overall look and the global shape of the world (which is really interesting to look at ^^)
I'm not sure I get what the blank part is though. Is it snow?
For me the mountains are a little weird in some places. Mountains are created where there is volcanism or tectonic forces in action. So there is a logic behind there placement. Often the mountains will be dispatched on some kind of line. I think about the mountain at the right of the little island in the middle as well as the mountains of the South. You can use real reliefs maps to have ideas of this: example of relief map
Also even in full size, I can't read the names of the cities ^^
Except for these, I think you've done a great job and it makes me want to know more about this world!