I think
Beth as a full name works fine. But
Beth can also be used in lots of awesome double-names, if you're into those!
What about Alyssa-Beth. It's almost
Elizabeth without the sounds you don't like! Too cheesy?
Bethany's nice too. I guess it's a bit more chic than
Beth, which has a very simple, rural vibe for me.
Bethany has that "cool old fashioned" feel, while
Beth is just old-fashioned.