Initially, I had some trouble getting this to work when Gmail officially released their new skins/themes. After some experimenting, I found that the add-on will look okay if you apply it after you have loaded Gmail's "space theme". Hope this helps.
The graphics won't load for me because they are hosted on their site, which is currently down. The graphics should have been made available within the extension. More than a speed issue (local graphics will definitely load faster), its a security issue of loading stuff from another site.