It’s been years since my MLA Guide disappeared in a heap of junk at the bottom of a locker, but I seem to remember hearing that if you referred to a work of art, you had to put in a works cited entry for it. Something that looked like:
Painting title. Artist. Year. Book it was found in, yadda yadda yadda.
I Googled and haven’t found anything. Am I imagining things again?
Name of artist. Title of work. Location, city. E.g.,
Renoir, Pierre-August. Girl with a Hoop. National Gallery, Washington, DC.
(N.B. I got this from a freshman comp textbook, not the official MLA stylebook, so you may want to double-check.)
An alternative: If possible you could put a copy in the painting as figure x, and then refer to it as (fig. x).
As far as there is a official format, Porcupine has it right. Are you actually deriving information from the painting? Generally, I think a good reference would include, artist, title, date (as much as we know), current location (museum/collection and city). I don’t know if there is an official format, but in art history this generally suffices.