This is a mythosaur skull—the symbol of the Mandalorian people, often found on their flags and stenciled on their armor. Often mistaken for a bantha skull by fans.
It is based on a ram skull wall decoration from The Sims Medieval, which was converted by evanesco over at Garden of Shadows. Appears under Decorations -→ Paintings.
Updated 1/12/2017 to fix a mistake with the GUID that was causing it to clash with the object it was cloned from. If you downloaded before, please redownload.