There's a post somewhere on here (aesthetic or pics maybe) of a guy who dyed his leather seats so they're 2 toned...I thought it looked pretty cool as he had the doors two toned as well. Looked nice and doesn't cost much to do if you have the cajones to try it. Also, if you're into the carbon fiber look you can buy sheets of the stuff off ebay and redo your dash area with carbon fiber. Here's some links also to some cool little ford and svt emblems you can put on your steering wheel or wherever.
http://www.muskatracing.com/muskatracing/id2.html
http://svtcustoms.tripod.com/svtmain/id7.html
All this stuff is relatively cheap and if done right IMO looks very nice.
Here's the link to that thead of the 2 toned interior.
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=picsvids&Number=324200&page=1&view=collapsed&sb=5&o=2&fpart=1
Although I notice you've got a GL so that would be cloth seats right? You could sill dye them with some other kind of dye I'm sure.