UPDATE: It's a pity that Posterous had to shut down and I regret that the article below is no longer relevant - Markk
The cool Posterous people have announced that users of their free sites can now customize the look and feel of their sites.
You can choose from built-in themes, customize colour and header image, and even write your own custom CSS/HTML themes.
Before, users are stuck by a minimalist look. Something like a plain Jane.
For those who have yet to sign up with Posterous, it's good for you to know that this is a free, simple blog/site and it's a breeze to set up. Check out my Posterous site here.
For starter, Posterous has come up with five built-in themes to choose from.
According to the Posterous site, they will be releasing more themes in the system "as soon as we create them."
Posterous themes are Tumblr-compatible. The Posterous Theme Engine was built to work with the thousands of existing Tumblr themes. - Markk
Way To Go With Posterous