This would require a workbench or some other mechanism within the crafting screen to modify but I'd love to be able to use trophies and other items more often. With boxes and boxes full of this item or that, even shared between multiple people, it can get a bit tedious having so much junk, only to use it once or twice.
I'm no artist so hopefully somebody could whip up some concept art?
Trophies could be put on the bow of the ship, or they could be used to put an image in a Jolly Roger-esque on the sail. Especially since skeletons are frickin EVERYWHERE. It'd just require a skull and two bone fragments, and if you wanted to put it on a black sail then you could use additional items for dye.
For the different colors, you can use the different trophies in combination with different items such as berries, just like with banners. We could get green from Draugr trophies or orange from ooze; that'd let you use it for more than arrows and grenades.
In fact, I'd say that this would create a want/need to revisit some areas when players feel they've gone stagnant. The way that me and my friends play entails a lot of aesthetics for the house so more things to play with will definitely add more game time played for us.