What type of camera is compatible with the Arduino Uno in which its pictures can be saved onto the SD card?
Something with an asynchronous serial or spi or (maybe?) i2c type of interface is probably going to be best.  The Arduino's ATMEGA is a fairly limited chip, so something that requires a lot of work to talk to, either because it is very primitive, or because it uses a complicated protocol like USB, is probably not  good choice.

Needless to say, don't expect high frame rates.

Realistically, by the time you buy the camera, the Arduino, and shield with the SDCARD there are probably more capable platforms to be had for the money, but if you know Arduino you would not be the first to add this combination of things to it.