That is very cool. I have a couple of suggestions though. Firstly, when you mouse over the name comes up. This is great. However it should fade away when you move your mouse away again. As it is, the name stays up.
Also, I'm not sure a standard Times New Roman(-esque) quite fits with the beautiful hand-drawn style of the map.
I think your towns need to be made a bit more obvious. At that scale they are hard to distinguish and can easily be missed. I'd suggest a couple of clear angular highlights. The angles would stand out agains the softer lines of the map, and the highlights would bring them out from the tonal range of the other regions. The tower stands out nicely for this region. The tonal range is very different from the areas around. The towns to the south of the tower are hard to find because their tones are almost identical to those in the mountain range - particularly the one at the end of the mountain range to the SW.
I think the interactive nature of the map is awesome. It's something I've always thought was a great idea for a map, and this one does it brilliantly. Any chance of a tute on setting up the javascript behind this? Please?