Leaked pictures of the Samsung Galaxy S4 surfaced earlier today. (March 11th)
Judging from these images, the device will bear a striking resemblance to the Galaxy Note 2, which was released towards the end of last year. The pictures were leaked by a well known Chinese forum known as Sammyhub. They do not appear to be photoshopped, but they could just be another prototype model that Samsung might have been testing at some point. Samsung also did this with the Galaxy S3.