Whilst certain materials can be produced in reasonable thicknesses, PVC and MDF for example. Generally, if you want to enhance the quality feel of your signage, the simplest thing to do is use either aluminium or aluminium composite to add a rebate or depth to your sign.
This edge can be any depth, but is normally 50-100mm; an Image can be added to the face as well as the edge if required.
It will then need to be fitted on-site. With trays, you would normally first fit top and bottom strips of aluminium angle to the wall, onto which the tray is then bolted. The top edge being hidden from the viewer and the bottom fixings minimised to maintain a quality display.