Ok so the idea of crafting a banner with a shield to get a decorated shield is a really awesome one in theory, but in reality it is disgusting.
You can craft a pretty decent banner and put it on a shield and it instantly looks like a completely different thing. Doesn't work at all for using banners as a sort of 'Coat of Arms'. This is what happens when you downsize 20x40 to 10x20 for the purpose of fitting it on a shield. Please, make the shield banner patterns the same size as banners! Otherwise this feature is completely unusable! I put this on the feedback website and it collected 300 votes before they removed it and said it should go on here instead.
Duplicate of MC-86135