Suitable board material for picture project.

[boscawen46]

Hi,
I sell framed prints and a future range will be thin metal plaques about 30 x 40 cm with designs on them. I want to adhere them to a backing board which I need to be an off white colour and then put a frame around the board. There will be a border around the plaque of about 2 inches. There will be no glass or perspex etc simply the plaque on the board. I'm happy to paint the board a suitable colour but can anyone suggest a relatively light, affordable , stable (non warping) material ? If there is already an off white one I would prefer it too be Matt not gloss.
I guess I am looking at about 3-4 mm ?
Thanks in advance
James

[prospero]

I would lean towards MDF - maybe 6mm. You can paint it with artists' acrylic paint, maybe 2 coats minimum.
It would be a good idea to give the backs (and edges) a couple of coats of varnish to waterproof it.

[JFeig]

The term "a thin metal plaque" covers a broad arena.
Have you considered using wide wood fillets (liners), about 65-70 mm wide, similar to fabric covered ones for stretched paintings? Your work can be attached to the top inside edge of them similar to a tray frame. Some of these come pre-primed for painting.

[technoframer]

Foamex aka Foam PVC.

[boscawen46]

Thanks very much for your responses all. The " plaque I am using is simply a thin metal sheet 40 x 30 cm and about 2.5 mm thick. I want to purposely stick it to the board so that it is not proud of the frame at the front. I have already done this with pictures before. My question was really about the board I could use. I had thought of 6 mm MDF but transporting quite a few pictures would end up being quite heavy. As suggested Foamez would be great but wondered if it dents easily ?
Thanks again.
J