Consider that one of the challenges to early Photoshop was be doing graphics manipulation that is right at the edge of what the hardware at the time is capable of, I don't think that stuffing a relational database engine between the raw bits and the drive would be helpful.

The challenge needs to add the condition of the app stretching the hardware capabilities so hard that a whole pile of not-so-clean optimization tricks are necessary to get the performance up to the acceptable level.