Friendicas user interface is easily theme able using Smarty3 templates for layouts. It ships with a handful of themes, and many more are available at friendica-themes.com.
Vier is the default theme of Friendica since version 3.5.
Profile page of the UX Watchdogs forum using the Vier theme.
Community page of the snarl.de node using the Vier theme.
Display of public events of the Berliner Luft forum using the Vier theme.
Display details of an event of the Berliner Luft forum using the Vier theme.
The follow up theme from Duepunto Zero was the Quattro theme.
Profile page of the Friendica Hackathon forum using the Quattro theme.
The old default theme of Friendica until version 3.5 was Duepunto Zero.
Screenshot of the timeline of the user meeting forum, which uses the Duepunto Zero theme.
A new experimental theme, which is shipped with Friendica since version 3.5 is the frio theme.
Display of a user profile using the frio theme.
Display of profile information using the frio theme.
Display of the photo gallery overview page using the frio theme.