A modular wall overlay system for installation on a support surface includes a frame; a cover that is securely, yet detachably, retained on and along a front face of the frame by a tensioning mechanism that is configured to tension the cover; and elastic corner inserts that are disposed in corners of the frame and include curved outer surfaces that are configured to permit the cover to be stretched over the elastic corner inserts creating radiused corners and preventing tearing of the cover in corners thereof when the cover is tensioned by the tensioning mechanism.