Irock is right.
Blizzard's mapping style isn't the detailed and complex style we're used to, it's a more bare and efficient style that suits him as a programmer.
The big point to this game is the story is fun to play through, and the battle system has unique quirks that separate it from the standard without being unfamiliar. Oh yeah, and minigames, lots of those.
I agree that the maps could use a little sprucing up, and there are dissonant colors and fonts and battler styles and etc... but I think that making a 20 hour game into an 80mb project just so that it's easier for people to download is worth the sparse mapping, and let's face it, Blizzard likes the color scheme how it is. We might not find it as pleasing to the eyes but we're not the developer are we?
Criticism has been noted, there's no reason to beat it into the dertt.
As far as windowskins go, iirc Blizzard made it so that you could use your own windowskin if you wanted to so that's really a non-issue.