I agree with Mibi here.
This has definitely got the workings of a fine battle map, and long has.
As for specifics...Hm...I'll start from the bottom of the map and work up!
Lets take a look at the legend. Of course, the use of the airplanes and ships are unique continent distinguishers...I like them. I'd be nice if we could pretty up the font on each, but I don't think there is ample room to do that. As for the flags, I like the idea, but perhaps not those graphics you have. Right now, you've got a very hand drawn effect on the map...take a look at the plane and ship icons, along with how the continent looks. The real graphic images of the flags seem to stick out a little. So perhaps if you found a graphic that reflected that some how, it could mesh it all a little more. Or you could also create your own flag files from scratch too!
The battleship (I think it is, isn't it?
) looks a little odd. I think it may be suffering from what the flags are, or something similar. Maybe look into a different style of image or perhaps simply playing with the color and hue and such.
As for the sea, it is different, I'll give you that. I like the color, or something similar to it, but the current ripples I'm not sure about. But I'm not exactly sure what other textures you have that would look better!
The font for country names could be improved. Maybe with a touch of boldness? Or perhaps a slightly different font. I do like the current font, because it is easily read, but I think it could stand out a little more. And maybe be a little more eye appealing.
Hm, I hope to look a little closer at the gameplay soon...!
--Andy