If they are on your computer (even if you deleted them) there are programmes available that will retrieve them if possible. When you delete a file from your computer, its not totally removed (even if you delete from the recycle bin), its simply written over.
Its also worth plugging in your digital camera (if thats where you got the pictures off) and running the software on that. I've done similar things when I deleted songs/videos off my iPod and was able to recover them.
The programmes that are freely available off the internet will bring them back, though they may have been written over.