Sooner or later, your business will need at least a few images. Supposing you can’t afford to pay a visual artist, photographer or graphic designer to help you create the visual elements you need. You don’t want to just take the first decent image out of Google Image search. Why?
You probably don’t have the permission to use it
You’re probably financially responsible if the copyright owner decides to collect
Disclaimers, back-links and credits are meaningless without licenses
The obvious solution of course, is to buy stock images and their associated licenses. Unfortunately, not everyone has the cash to spare for this sort of thing. This is where you start looking into images covered under Public Domain and Creative Commons licenses. Here is an ultimate freebies list.