If you want something that is free you can try Recuva from Piriform. Of course there is a paid professional version available as well. I have used the free version of Recuva and it has worked well. As plyren mentioned the chances of recovery are diminished if the pictures have been overwritten with other pictures. As for the software mentioned in the link provided by plyren and according to the site the free version will allow for recovery of up to 2 GB. Anything more than that and you will need to purchase the software.