Cosmetics Beds is a mod that allows players to add banner patterns to their beds, kind of like what they can already do with shields. This is done simply by crafting a bed with the desired banner. The banner pattern will encompass the entire bed, so the color of the bed doesn't really matter as much as the color of the banner when they're combined.
In addition, players can separate them again by crafting the decorated bed by itself. This will yield the original banner used and will leave the original bed used in the crafting grid.