By and large, the best option is to choose a backplate that matches the design of the door handle itself. However, a contrast look many also work well. The size of the backplate can also vary but it should be generally in proportion to the handle. In case you are using the plate to cover marks or holes left by an earlier latch mechanism or screw holes, it is safer to first get the backplate of the right size and then buy the door handle that will go with it. If the door has a keyhole, fit a plate that is resistant to scratches caused by keys rubbing around the keyhole area.