Mac: The Dropbox syncing icon is a handy way to easily see what folders are synced to Dropbox. If you don't like the boring old Dropbox checkmark, Jacob Salmela shows how to change it. One the surface, the process simply requires you to replace one set of icons with another. Of course, it's not exactly that simple, especially if you want it to look good. For that, you'll need to edit the existing icons and drop in high quality versions of your own. Salmela shows how to do this using Pixelmator, though it should be doable in just about any image editing program. Head over to Salmela's site for the full guide.
Customise the Dropbox Syncing Icon to Whatever You Want [Jacob Salmela]