Aside from the all purpose scum, there don’t seem to be many derogatory terms used in the SW universe, at least not heard on screen.
Well, both the movies and the EU have had some pretty interesting swear words over the years, although very few of them are real-life curses;
http://scifi.about.com/od/starwarsglossaryandfaq/a/SWAR_curses-and-expletives.htm
(My favorite is “Sith-spit!”)