When I wanted more images, I just started googling terms like "backgrounds," "icons," "symbols," and "buttons." I was amazed at all the stuff I found. Most of it seems geared toward the web design/graphic design crowd, but that's okay, as it works just fine for our purposes. I downloaded a ton of stuff and organized it into my REMOTE DOWNLOADS folder as buttons, backgrounds, product images, etc. Now I have all these great graphics available when I'm programmnig.

By the way, in case you haven't found it yet, there are some free downloads on http://www.guifx.com/