New themes will be coming in the next PS4 update, Sony have confirmed.
At their Pre-Tokyo Games Show press conference, Sony showed off some of the themes, demonstrating how they're dynamic and interactive, and will be customisable by the user.
The video below shows off Sony's Japanese mascot theme:
The next update (Firmware 2.0) will also introduce Share Play, which is a way for users to share their game with another friend via PSN for 60 minutes at a time.
Unfortunately, no release date was given for the new firmware update.