Commercial use of public domain pictures
It depends on where you are selling and who made the photo. 

https://commons.m.wikimedia.org/wiki/Commons:Reuse_of_PD-Art_photographs

In particular Germany and Norway will be tricky... if you can source the photographs and get the creator of the photograph to license the photo to you, you will be in a good position. This is because even thought the original painting is probably in the public domain, the photographer has their own rights...