Hi Anne! Thanks for the nudge - I need to redo the Family History Photo of the Week project page to explain the changes since we implemented the photo sharing feature.
In a nutshell though, anyone can share photos to the G2G with the photo sharing feature. Every Wednesday I gather up the ones that qualify for the Photo of the Week contest and post an album on Facebook for people to vote. Every Friday, those votes along with the G2G votes and the G+1 votes on the photo page are counted to determine the winner.