Whats the prettiest BART stop on the East Bay side?
If you think the Berkeley BART stops are "pretty", that's interesting. Beside being underground, homeless people and what they leave behind, I find most of the original BART stations fairly gross. The "nicest" stations are the newer ones... so... Fremont or SFO. I like the Walnut Creek BART station area with the buildings... but constructions starting there so the station itself will be a bit of a pain, but the surroundings are nice. If you have not finalized all your arrangements and if it makes sense for what you want to do, it might be worth staying at the Embassy Suites in Pleasant Hill or Renaissance / Club Sport (across the street from the P-Hill/Contra Costa Centre BART station and use it as your "home base" rather than Berkeley.
Walnut Creek is probably the one with the most to do right near the station. It's pretty white, if that matters one way or another.
Really all I can think of on that side is Walnut Creek and that's not something I'd write home about. One would think that BART would have destinations near their stations like other places. Sadly it doesn't. You could go to Pleasanton to a mall. It's a nice mall, but still just a mall. Fremont has a newer area you can walk to, but it's nothing I'd ride that far for. If it were me, I'd be spending my time in SF and just going back to the East Bay to sleep. --edit-- and, yes, your question was very oddly written and made it sound like you actually wanted pretty stations; not areas around it.
Rockridge is near a wonderful neighborhood full of shops, restaurants and bars. Another nice stop is Lake Merrit you can stroll around the lake, catch a movie at The Grand Lake Theater. 19st Oakland is an ok stop during the day but most of the restaurants close early. There are two performance venues near the station the Fox [live music], and the Paramount [Music, and film].