We didn't make this word up. Honest. It's a stone age cave painting. The dictionary definition is "writing on stone" (two roots: petro means stone, and glyph means writing), and along with "pictographs", they are often described as "rock art." Technically, petroglyphs are made by scratching away at the rock and pictographs are made by painting on the rock.
We have a national park (well, "we" in the general sense), Petroglyph National Monument, in New Mexico — a fine place to go to learn about these ancient artworks. You can also find them in Hawaii, in the American Southwest, and along the central coast of California. That's where we're from. The word petroglyph is very visual, evokes a sense of creativity without "artistic pretense", and given a little creative license, could nicely describe painting on ceramics.
Perhaps more importantly: a petroglyph was a personal statement, an early form of individual expression, story telling and creativity. It was a magical time in history, where people lived with the Earth, had discovered art and written communication, and lived in small communities. Aside from avoiding hypothermia, surviving childbirth, and not being gored by a mastodon, it was probably a great time on Earth. Anyway, it's the name we chose for our business. Leave your mark on the place where you live.