The concern with the rivers is that they don't go anywhere, the way this map looks. Of course, rivers empty into the sea, but here they don't appear to.

It also doesn't look like the start anywhere (rivers are fed primarily by snow-melt and rain runoff from mountains and possibly from springs and other sources like that).

Finally, rivers merge together from feeder streams, typically not branching until they reach the sea.

From the map here, I can possibly guess that the rivers are emptying into a couple lakes, but I can't see any reasoning why the lake then doesn't feed something that empties into the ocean.

Otherwise, it's a good start working in GIMP on this style of map (I style I am slowly trying to work through myself).