Hey,
Started to throw around some ideas. I'm thinking about something to do with colour.
Here are some sites I looked at for some inspiration:
http://psychology.about.com/od/sensationandperception/a/colorpsych.htm
http://www.infoplease.com/spot/colors1.html
http://www.squidoo.com/colorexpert

I found looking at how colour effects your mood really interesting. The sites talked about differen colours and how human react to those colours. I'd like to better understand how they reached these conclusions and why we react to the colours the way we do.

Anyway, still thinking...