Apple has released the first update to the public beta that was released last month. Unlike the developer version, the public beta is not regularly updated, so this should bring quite a few changes.
The Yosemite public beta 2 is essentially the same as the developer preview 6 that was released earlier this week. It has several design changes, including new iconography throughout the UI (nothing you saw until now was finalized and things keep changing in the betas), new wallpapers, and some other bug fixes and general improvements.
Along with pushing the beta 2, Apple also released iTunes 12 for Yosemite. The new app has a redesigned UI that looks less like a flattened version of the iTunes on Mavericks and more like a new app.
If you are running Yosemite public beta on your Mac, you can get the updates from the Mac App Store.