One of the things I gave up in moving from WordPress classic to WordPress.com is theme editing. My previous blog had its own theme, or rather, user-switchable family of themes.
I’ve started off here with the Simpla theme. I’ve customized the CSS a little; for example, I’ve floated images at the right of posts. I’ve used widgets to build a different sidebar.
Lovely though Simpla is, I think I’ll be using a certain different theme before too long. The Sandbox is a theme for themers.