To contact Lucasfilm regarding the use of their trademarks, send a letter to the attention of their Publicity Department at the following address:
P.O. Box 10228
San Rafael, CA 94912
Good luck.
I'm glad this was brought up, actually--because there's this RV dealer here in The Okay State that is using the Indiana Jones theme in their advertisements.
Bugs the hell out of me every time I see it--not only are they using it (which I assume they don't have consent for), but they're also chopping the hell out of it.
I was trying to decide if I should contact someone about it, and this looks like a good place to start.
Hopefully Kerr Country RV will be joining the esteemed ranks of C & D-recipients, along with Chris Berry and Luke Skyywalker. . .