A radiolucent mat includes a strap system configured to secure the radiolucent mat to an image receptor, and a body portion extending along orthogonal length and width directions of the body portion and including a top major surface configured to face away from the image receptor. The top major surface includes one or more first visual indicia delineating a region of the top major surface corresponding to an active region of the image receptor. An image receptor assembly includes the radiolucent mat and a radiography image receptor having an active region. The body portion is disposed on the image receptor such that the body portion and the image receptor are substantially coextensive with one another along the length and width directions.