I think its a noble first effort. As has been said before, I think the land is a bit to small for all the geographic features you have. For instance I think that having a desert of any kind on such a small island is a bit of a stretch. Also, mountains are rarely stand alone affairs (regardless of what Tolkien may say ). For that reason, it seems that the large mountain in the center should be more connected with the northern range.

However, having said all that, this looks like a very fantastical land, and the standard geophysics may not apply. Hell, just look at Tolkien's Middle-Earth for example. On his maps the rivers Celduin and Anduin both have very close origins (even the same origin in a few maps I've seen) in the Ered Mithrin. These two rivers flow in different directions, however, despite both being from the same side of a continental divide, with the Anduin flowing south (hugging the Misty Mountains, might I add, also an anomaly) while the Celduin runs through Mirkwood to Dale and eventually to the inland sea of Rhun. What I'm trying to say is that, if your map corresponds to a fantasy world that is not bound by our science (Ea, the "planet" Middle Earth is on is flat, after all) then all of these worries do not matter as much. But the map will also by force look "unrealistic" by those same standards. If it fits the logic of your story, I wouldn't change anything.

And yes, I do second the idea of trying out more organic map creation methods with GIMP and Inkscape. A dedicated mapping software has some benefits (built in support for fractal coastlines, for example) but overall, learning the more advanced tools will give you more control over the results and be useful for more than just maps, too. Keep up the good work.