It looks very nice! I always found Modpodge to remail a bit soft and slightly sticky ( used it over decals and images on board or woodworks). I always used a casting resin in 3 layers minimum, tinting each layer from dark to light with a hint of green and blue, up to a clear top coat... Adds a great deal of depth but is messy and takes a long time, as well as a risk that it will warp from the heat produced and pull your layout apart. As far as your technique, apart from the lack of visual depth ( judging by the pix here), the effect is virtually the same with a great deal less work or mess!!