Mountains are almost ubiquitous in fantasy maps, and almost always drawn in profile, as a line of hill signs. In a Patreon post, mapmaker John Wyatt Greenlee (aka the Surprised Eel Historian) discusses a couple of ways to draw mountains and mountain ranges in the usual fantasy map style.

See also his post about the mountains in maps he draws for his academic clients, i.e., maps that appear in academic monographs. (“Some academics don’t want mountains. Some want icons. And some want topography. But some brave souls want full-on Tolkienesque mountain ranges.”)