Nice idea and done very well. I would only say that the brightness of the interior is not settling good with me for some reason. I would try just toning down the lightness of the "bottom layer" ? the interior and maybe try even desaturating it so that the colors of the door are more effective. As a side note, possibly even adding some vignetting to the outside areas of the frame would bring us in to the peephole. A good idea and done well.