Blog Me, UK! has currently well over 1,500 themes to choose from for your blog. These have been collected from various sources on the web, particularly:
As the built-in themes browser shows all these themes on a single page, you may find it easier to click on the links above and choose a theme, then come back to your new blog and select it from the Design ⇒ Themes page.
If you would like any other publicly-available theme to be installed, either mail me or leave a comment here with the URL of the theme and I’ll see what I can do.
As themes are shared among the Blog Me, UK! web sites, you cannot currently edit a theme for your own site. This facility will be available shortly to Gold Members. But remember, most newer themes allow widgets to be installed into one or more sidebars, allowing a fair amount of simple customisation.