From here: http://www.slrlounge.com/women-classic-paintings-get-photoshopped-fit-todays-standards?mc_cid=3d24104991&mc_eid=7c9a2dbb22
Please note that the link takes you to classics that do contain nudes...
"Photo editor Lauren Wade has seen and preformed many a Photoshop retouch having worked in the industry for 5 years. A little nip there, a little tuck here, it is the standard of beauty these days to see gaunt models airbrushed to perfection. No thigh gaps, double chins or a blemish to be found…perfection. Just like a mannequin. Yet, this was not always the case. Throughout history, and even in recent history, a size zero woman was not upheld as the norm. Going back throughout art history, famous painters from Degas, to Raphael to Botticelli depicted curvy women, with bellies and “imperfections” that the modern magazines would “fix” with some quick clicks in Photoshop."
To see more works of art being modified to perfection, check out Lauren’s article over at TakePart.