It is always a good idea to make backup of your pictures to your computer or using some cloud sync solution as Dropbox to make your pictures safe.
But not everybody does that. If you don’t, consider start doing it.
I friend of mine was bored because her smartphone was slow (Samsung Gran Prime DUOS) and she cannot take pictures or record video without waiting a long time.
Then I decided to do Factory Reset for her, but I didn’t backup her pictures, then when we restarted the Android only the old picture from external memory card (2GB disk) was there, all other pictures were lost!
I decided to recovery all file for disk and searching in the internet I found this nice tutorial: http://dflund.se/~jokke/androidfilerecovery/
Unfortunately after download the raw content of /dev/block/mmcblk0 and running the “testdisk” program I noticed that the partition was not shown.