Ruin Explorer
Legend
Not only a module, but an elaborate reference in a China Mieville novel too, that piece of art is basically at the center of one of the characters' world views in the novel Kraken.So good, it inspired a module.
Honestly, paladin would probably have been my favorite class even without this picture, but it sealed the deal for me. The lone hero battling against the hordes of evil? Sign me up!
I'm actually having trouble thinking of a specific example for a class in D&D, weirdly enough. A lot of stuff inspired me to play specific races or specific kits - ooooh how about Speciality Priests? The Priest of Mask image and description from Forgotten Realms Adventures back in the day convinced me to play that as my very first D&D character.
Unfortunately I'm having difficulty sourcing a decent copy. I'll add one later if I can.