Mid-sized black plate options I'm looking for a mid-sized (16x16, 20x20 ish) black plate for mounting on a wall. It can be a regular plate or baseplate since what I am mounting it on is not Lego and it doesn't need to fit into studs underneath.

So far I have only found this piece but no-one seems to sell it in black

http://alpha.bricklink.com/pages/clone/catalogitem.page?P=91405

Are there other pieces I should consider?
You can piece together a 16x16 black plate in two layers, by making a base layer consisting of 3867 - Baseplate 16 x 16 (not available in black, but Dark Bluish Gray is a good option and given the minimal thickness it won't show)

 

and then putting 4 of 41539 - Plate 8 x 8 in Black on top side-by-side.