A modular framing system comprises plastic components that each comprise a single article having unitary construction and which are connectable to form various sized SEG frames. Four unitarily molded corner frame connections each include protrusions receivable by at least four side rails, each of which may be unitarily extruded with a constant profile along the respective lengths of the side rails. The interconnected corner frame connections and side rails define a continuous conduit about the quadrilateral frame for receiving therein respective edges of the tensionable textile. For use with larger tensionable textiles, additional side rails and T-frame connections may be utilized, with each of the T-frame connections comprising a single molded article having unitary construction. At least the frame connections (both corner frame connections and T-frame connections) may be reused for frames of other sizes.