According to BishopThomas R. Valletta someone who does something related closely enough to the church that he has an lds.org email address confirmed in an email (to someone I don't know but that is circling the internet) that this photo could, perhaps, maybe, possibly be the only known photo of the prophet Joseph Smith.

In his words:

It is in dispute and there is quite a controversy surrounding it. The official position of the Church History Department is “we do not know.” Its main proponent is Ron Romig the Community of Christ historian who owns it.

To me, it doesn't look much like the paintings we have. But, then again, they are just paintings. It would be such fun if it is found to be authentic.