How do I retreive a lost iPhone application?

I just received my 16Gb iPhone, great! It is now unlocked/jailbroken but I have of some reason lost the “Pictures” application. It is not only gone from the Spring Board but from the file system itself. I think it should be possible to get a copy of this folder from another iPhone owner and just add it to my device. Does anyone want to help out having an iPhone? Or does somebody have a solution how to restore this application?