There are some programs that can assist you in trying to recover the deleted photos. The procedure is simple, but the amount of recovered photos may vary. Among the programs I tested, I got the best result in the recovery was PhotoRec, you can get the installer for Windows, Linux and Mac OS X at this link . Ideally, the recovery procedure is performed as soon as possible to increase the likelihood of files retrieved by the program.
PhotoRec is a free and open source file carver data recovery software tool designed to recover lost files from digital camera memory (CompactFlash, Memory Stick, Secure Digital, SmartMedia, Microdrive, MMC, USB flash drives, etc.), hard disks and CD-ROMs. It recovers most common photo formats, including JPEG, and also recovers audio files including MP3, document formats such as OpenDocument, Microsoft Office, PDF and HTML, and archive formats including ZIP. 
PhotoRec does not attempt to write to the damaged media the user is about to recover from. Recovered files are instead written to the directory from which PhotoRec is run, any other directory may be chosen. It can be used for data recovery or in a digital forensics context. PhotoRec is shipped with TestDisk.
PhotoRec is compatible with:
DOS (either real or in a Windows 9x DOS box) Microsoft Windows: NT4, 2000, XP, 2003, 2008, Vista, Windows 7 GNU/Linux FreeBSD, NetBSD, OpenBSD SunOS Mac OS X