well..pictures and other media files are saved on the flash memory so it's not difficult to access to them.
if you already have a recovery you can access to memory by:
pwr+vol up > in fastboot select recovery with volume buttons and confirm with power.
once you get into recovery go to memory and storage> at the end of the list you find "mount usb storage">connect phone with usb to a pc and save img/photo and other things.
if you don't have it you can flash it, it won't compromise your data.
if you are looking a way to save data from apps such messages and other things similar, follow the procedure on developers.google.com to flash the rom but stop it before erasing the memory and re-flashing the rom; one time the same thing happens to a friend and this have "unlocked" the device so it have completed the boot and allow to save everything before flashing the new rom
hope this will be helpful..