I have found a surprising assortment of professional photos and images on some of the installation CDs for various programs. If you keep your old CDs you might browse the folders. Among those that proved to be a reasure trove:

Photoshop (5.5 had a real nice assortment) - U-lead image browser. - Old printer CD's (Canon and HP both yielded some) - CDs that came with scanners. - Subscription to Dynamic Graphics gives you a CD with lots of goodies. - Print Artist - Printshop has a lot, but most are very low-rez, some have excessive .jpg compression ruining them completely. What were they thinking?

Some of the graphics program training books like have some. Photo companies put them with many programs as a form of advertising to graphic artists.

Microsoft Office comes with a slew of images in the clipart folder, and their website has many nice images for registered Office users.

FrontPage 2000 CD-2 had a bunch of cool images where an object is extracted from the background and stored as a layer, but they are in a .mic format. But the  MS image composer on that CD allowed me to save them as .tif with the layer intact. etc. etc.