my advice?- fuck customize. almost none of the themes on customize have the right installation encryptions so they simply dont apply to the ipod, they just use up memory. if you haven't already updated to the 2.0 firmware, i suggest doing so, its way worth it.
to get themes, (on 2.0) use cydia. make sure you have winterboard installed, and once you have that you can download tons of legit themes off cydia, just go to sections and scroll down to themes. once you download a theme, just open up cydia and select the theme you want. what i did to make my theme is kind of advanced, and i was able to customize every icon and the wallpaper, but if u want to learn how to do that i'd be glad to help.