Getting images from web is so easy, we tend to forget someone created image and should be paid for use of it. The first thing you should do when considering using one, is getting permission from creator/designer of graphic or image.

You have to read user agreement carefully before using images offered by some websites. Most of time, they are free for personal use but must be purchased for business use.

There are many distributors of commercial graphics and images catering to needs of Webmasters. Some come in sets of multiple indexed CD-ROM's with a searchable database.

Another good source is return bin of retail computer goods stores, such as: CompUSA, Fry's and so on. I've found huge collections of commercial graphics for next to nothing because somebody opened package and brought it back for a refund.

Likewise, your digital camera can be a source of royalty free images. A word of warning: You still have to get permission from owner of any commercially protected product you photograph; just because you photograph something doesn't mean you own all rights to image.