Armour wallpaper? Go to the scrap yard and ask for a sheet of 20mm thick plate iron. Might be a bit heavy after you stick it on though, might have to screw in a support arm or something. How do you plan on seeing the screen after you hang the wallpaper?
Seriously, pic your poison. Go to www.google.com and go to images then advanced image search. Type the vehicle name in the 'exact' space and go down to size and click on 'large' or 'wallpaper'. Search away. When you find one you like,click onto the thumbnail pic to open that site (or go to the full size pic by clicking on the thumbnail when the site page starts to download) and when up just right click on the full size image and save to a folder. Open the pic in that folder, right click on it and choose set as wallpaper as the option - Bob's you Aunty.
If you can't find a large pic, maybe you can build a collage in Paint, just use a few pics and paste em in- save as a .jpg instead of .bmp to save memory.