Do you live near an art college? Why not approach your local photography students and ask them to do some discount or pro-bono work for them? You could offer to send other musicians their way, or just take them out for a night on the beer afterwards. You know what these students are like :p Offer them lifetime free entry to your gigs, or give them a copy of your CD, all of the above. You never know what talent you may find among the student population. Plus they'll have access to top equipment, so the quality's likely to be good.
Another thing you could try is inviting the local press to one of your gigs. I used to work for my local rag, and they always needed bits and bobs to fill up the ents pages. If a photographer comes along, you'll be able to buy copies of the photos from them afterwards. You may need to check the legality of using these pics in promotional or other publicly available media though.
