Little Big Men Studios have released several 28mm Wars of the Roses banners.
From their website:
Just finished two more Wars of the Roses Banner sheets. WOTR 3 is Lancastrian and depicts the swallow tailed banners of Somerset, Clifford, Devon and Northumberland, WOTR 4 is Yorkist and portrays the swallow tailed banners of Edward iv as at Towton, Warwick, Fauconberg and Norfolk. I have also done some livery badges on these sheets, between 40 and 50 per noble. These work in the same way as my shield transfers. So even if you prime your figures black, prime the area on the breast of the figure white and then apply the transfer.
You can then paint to the edge of the transfer so it blends in. I have done a darker colour around the designs to match the base colour of the livery to make it easier to butt the paint up to the edge of the design. These designs are around 0.25mm so will be fiddley to apply, a bit like transfers for small scale tanks. Also updated the site with a new Samnite design for A&A Miniatures, a new Celtic transfer for old Glory 28mm Celts and a Numidian sheet for Crusader Miniatures.