I reccomend looking at these sites if you are looking for huge photo galleries of hundreds of extreme vehicles.

Favorite Sites
www.supercars.com at supercars you can view all sorts of cars and concept cars.
www.streettrucks.com streettrucks has a lot of nice pics and they are also the creators of streetruck magazine.
www.socalcustoms.com This is the best place to go if you are looking for pics of show cars.