I mean, did you backed up your iPhoto Library to any external drives ?
Anyway I'm going to be honest with you. There is only a little chance of recovering the photos. Let me explain how this works. When you delete something from your Mac, only the reference to the files are deleted. The actual file will be there and it will over-written by new files when you keep using your Mac, just like you record on a tape. So it is still possible to recover them using Professional third part recovery applications.
So don't install any applications other than recoery applications and don't download anything like musics, movies etc until you recover them.
I can't guarantee the recovery applications will work, but its worth a try. The best recovery application out there is Data Rescue 3. Recovery applications are costly, so try the trial version before buying it. Get trial version of Data Rescue from here : http://www.prosofteng.com/downloads/download.php?prodID=78
Again, there is no direct solution for this problem. Your only option is to try the recovery application.
I know this is not the answer you've expected, but this is the only answer/solution to your problem. So, please don't rate me Bad or Poor if you are not satisfied.
If you have any questions or need any additional help, please don't hesitate to ask as I'm glad to continue to help you.