I am not a lawyer! That said: I’ve heard the rights holders for Conan may be a bit more on the litigious side, and there’s a recent RPG adaptation under official license by Modiphius. So—just to be safe—I personally would use a name other than “Conan” (and say “inspired by 1930s sword and sorcery pulp fiction, including R.E. Howard’s Conan stories” on the page). Then I’d scour public domain art resources (like comics and pulp magazines at Comic Book Plus) for anything at all that screams “Conan” to me, favoring things that match the “feel” of the game.