Hey hey, I like your simple art style! It actually fit's quite nice, although I'd say maybe get some more interesting land shapes in their (Circles are a good starting point, but as Holy Torstan once said, "If your line doesn’t look like it was plotted by a drunken ant, you’re doing it wrong.")
Other than that I would say, work on height representation, that's something difficult for me to put into words, but just get some mountainous looking things in there (not including your volcanoes-at least I assume they're volcanoes-cause they look great!) and also remember that rivers flow from highest point to lowest point, not across continents.
Other than that I wouldn't change too much, I think the simplicity of the map is one of its strong points.
I should also say, from one new guy to the next, welcome to the forums!
I almost forgot, you might wanna move this down to regional/world section if you still intend to work on it!