FPGA + Camera iamge sensors

Ok, but you don't want to read a prestored image?

A small image processing project, does this mean it is a small project or a small image? I take the latter to mean low resolution. You have already said you don't care much about the framerate, so then it is a matter of costs and available connections to the FPGA. Howmany IOs do you have available, which FPGA is on your board? I don't have a specific chip or camera to reccommend to you.

You might also want to take a look at some (free) IP that others have created to read from a camera.

It may be you can do what you want with an old consumer handheld camera that has video out, but that might require ad converters.