The DCMI (Digital Camera Interface) is indeed available on the STM32, but not in the 64-pin parts (used in Cerberus and Cerb40). It’s described in section 12 of the Technical Reference Manual for the STM32F405xx. If you were using the larger part, you could certainly write an unmanaged driver for it. It is capable of doing streaming video from the camera in various formats (including JPEG), and it’s also capable of doing single frame captures.
You’d probably have enough memory to do single-frame JPEG captures at low resolutions.
The DCMI interface uses DMA to move the data into memory very quickly. You’d almost certainly need to use DMA to move the data OUT of memory and into another peripheral (such as, for example, an SD card) or into another chunk of memory (external, as Gus said) fast enough to capture video at even low frame rates and low resolutions.
It’s an option I wouldn’t mind exploring, because good DCMI cameras are cheap (<$10 from SparkFun for a 1300x1040 JPEG camera), but it’s a lot of unmanaged work, and you almost certainly wouldn’t be able to do much of anything besides store the data. No image processing or anything like that.
For comparison, the LinkSprite camera is 640x480 JPEG, and it transfers data via the UART. It does still images only (unless you consider .3 fps to be video). It’s also $50 from SparkFun.