What is this common depiction of Ali ibn Abi Talib (ra), Hasan ibn Ali and Husayn ibn Ali in Shia islam based on?

Are their facial features, clothes etc. modelled after certain hadiths, if so which one? Also when did this start and how ISN'T this idolatry? Is it possible even that those aren't actual paintings dreamed up by an artist at some point but rather "paintings" traced after photographs of real people? (I've seen some photographs online, that looked eerily alike!)