Abstract: This paper introduces and presents a solution to the 'Escherization' problem: given a closed figure in the plane, find a new closed figure that is similar to the original and tiles the plane. Our solution works by using a simulated annealer to optimize over a parameterization of the "isohedral" tilings, a class of tilings that is flexible enough to encompass nearly all of Escher's own tilings, and yet simple enough to be encoded and explored by a computer. We also describe a representation for isohedral tilings that allows for highly interactive viewing and rendering. We demonstrate the use of these tools - along with several additional techniques for adding decorations to tilings - with a variety of original ornamental designs.