[dfc]

It seems like defaulting to readme content would make to many assumptions about the content of your readme.

[secoif]

Basically, it should just wrap the HTML generated from markdown (if readme is markdown) in some theme.

[dfc]

And oif your readme.md is merely:

"GPL Licensed"

The preview page will be much less impressive. As it is the preview page has enough lorem ipsum to give the user a feel for the theme.

[secoif]

Good point.