Yah, your best bet is aHome,Open Home, and DTX(or something like that) if your not rooted. They are not FULL themes but more like skins and don't change everything like the status bar at the top and some menus but do make it look better on the surface. If you want the FULL theme that covers EVERYTHING(for the most part) you would need to download the pre-themed rooted OS's..like Jesus Freak's, TheDude's, or Haykuro's. Its my understanding(i'm not claiming to be a dev,coder, anyone important) but Basicly, a dev/coder/someone will take those rooted OS's and run it thru the ANDROID SDK to change the pictures and icons and stuff, then re-package it to be installed on other phones...so by adding those "themes" your actualy installing the ENTIRE OS..not just changing the look. I'm using JF's 1.5 ADP with LucidREM's Apps2SD version and i'm using Open Home for themes. After I found out that the full themes where the entire OS i stopped using them. Cause people will sometimes screw up and your phone boot loops. Or it ends up missing a feature, or using a not correctly setup or signed OS version. Just easier to use Open Home.
