This was quite a bit more trouble than it should have been, but I am slowly getting the hang of Modo. So, modelled the frame, the matte, even a pane of glass, plus a plane for the photo of course. Then textured in Mari (except for the glass) and brought into Vue where I set the glass pane to a standard glass material, assigned a fairly basic colour to the matte, and textured the frame and the photo with the textures from Mari. I even got to create UDIMs in Modo that I could use in Mari. Yes, definitely moving along.
The modelling is pretty basic. No bevels on the frame for instance. And the texturing of the frame simply amounted to assigning four slightly different shades of brown to each of the four sides. Just getting the workflow to flow.