For stock photos try this link:
http://www.gettyimages.com
They're my first choice when I need a stock image since they carry almost every other stock image all on the one site.
For those who don't know what "stock images" are, they are used in the graphics biz when there isn't enough money in the budget to hire a real photographer. They have catalogs of pre-existing photos with a definite business bias - lots of scenes of people meeting, yapping on cellphones, shaking hands etc.
Technically, these photos are not free. You
are permitted to download small low-rez pics for use in layouts (meaning a design layout shown to a client to sell them on the idea). If you decide to use the photo in the final printed piece, then you pay for a hi-rez file.
However, since we modellers are never going to use the images for anything more than our personal use, inside buildings etc. there should be no problem with copyright.
If you print these out on transparent stock, you can use them as windows in your structures. Voila! Instant interior detailing!
Cheers
Val