If you plan to do B/W, I would suggest some more visual distinction on your water areas... I would not tell without your description. Some things you might try would be some simple waves or perhaps a woodcut effect on the parts tht should be water... The outline of the shore is kind of cool though.
One tip as you learn GIMP..... learn to use layers, lots of layers and learn to use layer masks on layers as you need them. I hope to post up a tutorial on layer masks tomorrow night so good time to pick up GIMP. Oh, and the tablet is a good buy. It will help you tons and if you are ever without it... you will be crying if trying to make a map.... Just ask Del... I thought we would have pitch in and send him some tissues while he was waiting on his new tablet to come in.