What appear to be scandalous in the eyes of the hard-liners are the exposed legs of a male model in front of female students who are making sketches.
The site claims the photographs demonstrate a lack of commitment to "moral and Islamic principles."
It says it has already warned against the activities of the center and adds that the "scandalous" pictures are merely an example of such behavior.
The website has apologized for posting the pictures while saying it hopes the move leads officials to deal with what it calls "cultural carelessness."
Men are not allowed to wear shorts or bermudas in public in the Islamic Republic of Iran (except during sports), where both sexes are expected to observe a strict state-imposed dress code.
Nude modeling is forbidden at official art classes in universities and elsewhere, and art students may only paint models who are clothed.
A friend of mine who studied painting in Tehran several years ago recalls that the only male model she and other female students were allowed to paint was "Baba Hassan," an elderly man in his late 70s or early 80s who was of course dressed when modeling. She says that the situation can be different in some private art classes, where she says she could work with models who were not fully dressed.
Iranian-French author and filmmaker Marjane Satrapi has a scene in her book "Persepolis" (which spawned the award-winning film) in which she and other art students are trying to learn about the human body and anatomy by drawing a model who is covered in a black chador and none of her body parts is visible.
While Reyonline and other hard-line sites who have reposted the report appear to be outraged by the pictures, for others, including a number of young Iranians who have shared the report and the pictures on Facebook and other websites, it has become a source of amusement and, for some, sadness.
This is how one young man reacted to the report: "They're just against arts; being outraged by such pictures is a cultural disgrace not the other way around."
-- Golnaz Esfandiari