Others may chime in, but I think the canvas needs to be acoustically transparent or the sound will reflect off of it and not be absorbed by the material underneath. I believe they have the ability to put any image on their canvas so you might could get the same picture, but it just wouldn't be the original.
As for the foam (and yes, you can certainly make your own), most use Owen Corning 703 foam that comes in 1", 2", and 4" varieties. OC703's specific use is for acoustic panels so it's purpose built for that use. You can also use Rockwool insulation. The thicker the panel the lower the frequency it will absorb.
7.4.4 Theater Room: JVC-RS500, Silver Ticket AT 2.35:1 142”, Onkyo RZ830, Anthem PVA-7, Panasonic DBT-110, JBL Studio 530’s, 4 - 15" DIY Sealed Subs
3.1 Living Room: Samsung 64” F8500 Plasma, Anthem MRX 300, Dynaudio Audience 52’s, Dynaudio Audience 122C, NHT SubOne