Map for George RR Martin's 'A Song of Ice and Fire', requesting critique and help

[galanix]

I am making a world map based on George RR Martin's A Song of Ice and Fire series (aka A Game of Thrones HBO series). They published official maps of this fantasy world a few months ago in poster form. That is what I am using for reference.

I want to do a complete vector-based map with hopes of making it into an interactive Java applet with pan/zoom functionality and toggleable layers. I did something quite similar to this a few months ago, only I made it as a Flash based app. You can see it here. In this updated version I'm going for a different look. I don't want to use vector icons for the forests, mountains and hills like I did before.

What I could use help with is how to best depict mountains, hills, canyons, and the various terrain. Since it is entirely vector-based I can't do something like shaded relief. I don't have extensive graphic design experience, and am somewhat new to using Illustrator, so if you have any suggestions I'd appreciate an in-depth explanation or a link to a tutorial. I also welcome any critiques you might have on what I've done so far. Thanks.