NOT clipart.com
My experience is that in the end its best to purchase on a per photo basis. While there are some nice deals out there for literally HUNDREDS OF THOUSANDS...if not millions of pics for lets say 199/mo...or 99/mo...or sometimes even less.....Over time you start to see how limited it makes your designs.
There are a # of places out there where you purchase per shot for 5-10 bucks depnding on what size you want and it gives you TONS of freedom. That is what I would reccomend