Firefox 3.6 now has Personas. These personas or 'skins' will customize your browser. I had a look at the Personas available (over 30,000) and did a search for kilt themed looks.

Tartans:
http://www.getpersonas.com/en-US/gal...x=0&search.y=0

Saltire:
http://www.getpersonas.com/en-US/gal...x=0&search.y=0

Scottish:
http://www.getpersonas.com/en-US/gal...x=0&search.y=0

Scotland:
http://www.getpersonas.com/en-US/gal...x=0&search.y=0

Anyway, if you're a FF user, you might want to have a look at these!