we never had a whole theme throughout rush... at our school everyone did a different theme every night.
Some examples of our themes:
Fire and Ice- one half of our suite would be fire, one half would be ice. Really fun to decorate for, and lots of fun foods you can use.
Party Animals- not what you think
This was when animal print was really trendy, it could probably still be used. Everyone wore animal print, the suite was decorated with a ton of animal print. We had a "bar" with different non-alcoholic drinks, it was made to look kind of like a club
At least at my school, these themes worked SO much better than some of the ones we'd used before, and some that seem to be popular. I remember when I rushed, i think there was a picnic theme one night.
It's all about standing out and being different from the other houses, and I think theme like this really helped us stand out against houses that did a camp theme, or baseball, or something like that.