I don't think there are any mixes that you need to stay away from.
I personally would not get a small dog mix, I would want something that is going to be at least 35 pounds when full grown. I would look for Border Collie mixes, GSD mixes, something cute, furry and of medium size.
Sinister ~ black GSD 3.11.09
Draven ~ Dalmatian 6.30.13