The painting in Hannibal’s dining room is Leda and the Swanby François Boucher created in 1740.
Leda was a queen of Sparta in Greek mythology. Zeus admired her beauty, transformed himself into a swan and seduced/raped her (this was obviously all right, because he is a god). The same night she also shared a bed with her husband, so there was not a conclusive way to find out who is the father of each of four children born from the resulting eggs. However, it is believed that one of the daughters - Helen of Troy - is the daughter of Zeus.
Leda and the Swan is common motive in both renaissance and baroque art. Other depictions can be found for example here.
It is a bit of bestiality porn, but it is all right as well, because it is art :-). I just have to wonder - if this is what have Hannibal in dining room… what paintings must be in his bedroom? ;)
It is also reference to Hannibal, the novel (thanks to reblogging fans to pointing it out):
“His absentee landlord apparently had a fixation on Leda and the Swan. The interspecies coupling was represented in no less than four bronzes of varying quality, the best a reproduction of Donatello, and eight paintings. One painting in particular delighted Dr. Lecter, and Ann Shingleton with its genius anatomical articulation and some real heat in the fucking.“
All descriptions of paintings in Hannibal are here.