Once you put your photos on Facebook, people are going to swipe them for their own use, and you can't stop it. If that scares you, don't put images on Facebook.
...OR!
Don't fight it; use it to your advantage. Put an unobtrusive but easily identified logo on every image you put on Facebook, and encourage people to share it and like it and use it. Post photos of people so that they tag themselves and share your photos. Your Facebook fans will become your marketing agents.
Don't put up any images that you expect to make future revenue; instead, put up images that you've already been paid for, or images for which you're not being directly paid, and use them as a marketing tool.
This really only works if your target clients are Facebook users. If your target clients are advertising executives and corporate media managers, then you're not going to get much traction with them on Facebook. If your target clients are teens, seniors, moms, etc - the people that are the "noisiest" on Facebook - then you can get a lot out of Facebook.