For shower bases for a mid century bathroom remodel, material is key. In post WW-II American homes, we see shower bases done in small mosaic-type tile (be sure the tiles you choose are specified for this use). I've also seen shower pans in preformed terrazzo -- still available today. Not sure I've ever seen one in an original mid century bathroom, but I also like the idea of porcelain-enameled cast iron and steel shower bases available today. Readers also have identified some modern materials that make for good proxies. Oh -- and we have shower door ideas here, too!