Your WPMU comes with the following default appearance on its homepage which you can customize for your site.
The homepage of your site is exactly the same as any other blog on your site. This means you can write posts, add pages, change themes, add widgets etc that provide information and tips to help your users. For example, the University of Blogs is the front page for Edublogs Campus sandpit site.
You can select from any different available theme and manipulate it how you see fit for your front page.
For example, you can choose to use a CMS theme like Nelo (pictured below).
and then customize it the same you would any other blog!
See next: Editing your site options