I'd set up a "sell your images" site to build a stock image catalog from. Have people create accounts in order to sell you their images with rights (this builds you a membership/email list you can tap later for additional money, these will be targeted towards digital photography/media) and offer between $0.25 and $1 per image (and keep your offers per image closer to the $0.25 point). BUT, set your minimum payout at $25.
Most people will sign up, submit a dozen or so images and then either lose interest or give up since you've offered them $0.50 per image and they'll have only accumulated $6 or so by this point. That's fine, they leave without collecting any money and you keep their images in your catalog.
Also, you don't have to accept every image submitted, so for members who stick with it and keep submitting, once they get close to the payout minimum start rejecting more submissions from them until you've started making money from the site, then make sure a few members reach their payout level and get paid. Highlite these members on the site to encourage more new members to join.
Get a couple hundred people like that and you'll quickly have thousands of stock images in your catalog, a decent email list to tap and it hasn't cost you much--if anything--at all.
For making money, you can do on-site advertising, promote digital photography and media affiliate products, AdSense and etc.
Also, you've got stock photography, sell licenses online and off. Web and print publishers are always looking for decent stock catalogs at reasonable rates. I know a local radio station that runs a simple monthly print newsletter and pays over $100 per month for a membership to a stock images gallery so they can fill the newsletter with decent illustrations.
If you hustle and look for every odd-ball opportunity to license the stock content out you can make a nice income from it. I'd suggest not even thinking about the mass publishers and marketing firms, but just go after the small offices, churches, groups/clubs and businesses that put out their own little monthly newsletters or reports and offer them a good rate for access to your "constantly growing" stock catalog.