The lovely brown hues in Eugene Delacroix's 1830 painting above, titled "Liberty Leading the People," were actually pigments made from ground-up mummies from Egypt. From National Geographic:
The use of mummy as a pigment most likely stemmed from an even more unusual use—as medicine. From the early medieval period, Europeans were ingesting and applying preparations of mummy to cure everything from epilepsy to stomach ailments. It's unclear whether Egyptian mummies were prized for the mistaken belief that they contained bitumen (the Arabic word for the sticky organic substance, which was also believed to have medicinal value, is mumiya), or whether Europeans believed that the preserved remains contained otherworldly powers.
What is clear to researchers is that early artist pigments were derived from medicines at the time, and were commonly sold alongside them in European apothecaries. And just as mummy was waning in popularity as a medical treatment, Napoleon's invasion of Egypt at the end of the 18th century unleashed a new wave of Egyptomania across the Continent.
Tourists brought entire mummies home to display in their living rooms, and mummy unwrapping parties became popular. Despite prohibitions against their removal, boatloads of mummies—both human and animal—were brought over from Egypt to serve as fuel for steam engines and fertilizer for crops, and as art supplies.
By the beginning of the 20th century, however, the supply of quality mummies for pigment appears to have dried up. A 1904 ad in the Daily Mail requests one "at a suitable price," adding: "Surely a 2,000-year-old mummy of an Egyptian monarch may be used for adorning a noble fresco in Westminster Hall…without giving offence to the ghost of the departed gentlemen or his descendants."
"Was This Masterpiece Painted With Ground Mummy?" (Nat Geo)