And let me know which template layout you like the best - i.e. travel, freestyle, kids...
What we do for a new theme is simply change the graphics - everything else stays the same, i.e. fonts, font colors, navigation menu, and layout of content. Many of these things you can change once you select the template and begin making your site, but some things you cannot change. In the Freestyle template you cannot change the navigation menu text at all (which I hated) so take that into consideration.
What I would do is take the template you like best and then make new graphics that fit the theme you want - i.e. patriotic, motorcycles, nascar, gothic, dog, cat, music, movies, whatever.
If you have graphics you like already, I can adjust them to work with the iWeb templates etc.
SB