Exciting Transparency!

Welcome to the world of images with transparent backgrounds! I have not exactly mastered them yet (as I don't really have the software to do them properly as of yet), but there's a few now on the site - the page icon (up in your browser's address bar) is now appropriately transparent, and the main navigation menu has just earned a logo next to the Home link... That last one, of course, brings up more questions than it solves - if I replace the Home link with it, will that confuse users? If I don't, where should it link? I also need a different image for the Antarctica/Quark Expeditions trip page... that's being harder for now!