If you want your player to partially see through an object, you'll need a transparent or semi-transparent material. Plastic film, cutouts, and grids are some of the artifacts you can produce with transparent texture maps.
For this recipe, we will create a material simulating a slide film. The main reason behind this choice is because this material will allows us to use full transparency to make rounded borders of the frame, and also use semi-transparency to illustrate the film itself. For the rest of this recipe, it is assumed you are capable of creating, using your image editor, an image like the one intended (basically, a beveled round-cornered rectangle containing a picture within). If not, please feel free to use the one included inside the 0423_03_04
folder.