Help, Ideas For "No More Round Numbers" Theme

Hi: I am looking for some ideas for a "No More Round Number Birthday Party"
I am throwing a 1/2 birthday party for my Mom, she is turning 59 1/2 this summer:-) We are having a pool party, most of the decorations have been focusing around tropical, that has been the easy party.
If I was able to come up with 1/2 or no round number theme, that would be a hoot! Any ideas? Thank you for reading my request.