The information you give is not enough, so I am not sure whether your pictures will be retrieved.
If you did not take any new pictures with your camera, then there is still hope, all you need is a kind of data recovery software. you can easily recover the deleted pictures with only a few clicks. BTW, this is a freeware and is simple.
But if the deleted pictures is rewritten, i am afraid there will be little hope to recover them.
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.