The delete button just unticks a box on each picture file. Nothing has actually been deleted.
As long as you don't overwrite the files by installing new programs and files, the info is still there.
There are loads of free data recovery programs out there, such as Aviraunerase (available as a free download from majorgeeks.com) piriform recuva, etc.
You may lose a couple of pics, but probably not. Programs tend to be installed on unallocated space, rather than space that has already been used before.