Simply said, a shadow box picture frame has at least one raised window mat that will cast a shadow on the artwork whereas a hasn't. In the example photo shown here the light blue mat is raised and casts a shadow over the child's artwork underneath. And while there are other matting and spacing variations, this is the main variation between the two styles. Again referring to the self-same illustration, many shadow box frames have one or more mats  recessed at the  bottom of the ...