Welcome to the Official BlackBerry Support Community Forums. This is your resource to discuss support topics with your peers, and learn from each other. New to the forum? Please visit the ‘Getting Started’ link below.
As aandras notes, there's no direct option for now. There's a decent chance the next major release of the OS will have support for attaching devices via USB as "mass storage" devices, in which case it might work then.
Until then, the simplest approach is, if you have a laptop or PC with a slot for the memory card, pop it in there and do a simple drag-and-drop of all the pictures from the flash card to the PlayBook's shared folders over WiFi.
If you don't have a slot, then doing the same thing with the camera attached to your PC via USB would be the next best thing.