Jeff,
The best single source (that I can think of) for old Las Vegas photos is UNLV Special Collections. Here's a link:

http://www.library.unlv.edu/speccol/

You can go to the library in Las Vegas, register as a guest, and browse through photo copies to your heart's content. If there's something that you want to see more clearly, they'll pull the original photo for you to look at. A photo that you want a copy of? They'll take your information, will make a negative of the photo (if they don't have one), and will mail the photo to you (with a bill ). Some photos are better quality than others, but it's a blast to look at them! We were only there once for a couple of hours, but it's something I'd like to do again sometime.

Something to do on your next trip to Vegas...