Chris is right. You need to have a story to tell about each picture you use as advertising. You'd hate to have a potential client ask you about a pic on your site and not know the circumstaces surrounding it. Someone calls and says: "boy that looked like a real pain to get that clean, how'd you do it?" Your answer is...Uh I dunno, click.
If you've got the courage to do it, the way I got some of my best shots getting started was actually approaching a homeowner, only after you've got your methods down after practicing by doing freebies for friends & family. For example: you notice an exceptionally nasty driveway in front of a nice home. Stop and present yourself to the h/o (only if it's legal in your area of coarse), and state that your looking to get some good b&a shots to put on your site and that their driveway would be a great addition. Offer your services at a discounted rate if you really want it.
I did this for a roof cleaning shot I wanted, a house I drove by everyday and knew I could really make it look good, and I still use them in a slideshow on my homepage.
