When you open up the inventory you see that all the hides the trapper has been collecting, and they are all exactly the same hide. My suggestion is just load the other .png files for the inventory. I mean in the stockpile they have their own texture, so why not follow through into the inventory.
There are different types of pelts for the same reason that there are different types of wood: because there are different types of creatures and plants for variety.
Though I’d love if the different pelts did make different materials, and we had different wood types that did have different colors.
I think for now they’re keeping it simple, with the two different types of wood making only one type of log that can be used for both light and dark colored planks. I would imagine as the game becomes more complex that they’ll eventually implement Oak and Juniper as separate logs. It’s difficult enough already to build things without having to worry overly much about aesthetics and counting how many of each tree you need to cut down to build your masterpiece.
it would be easy to add a new resource (with a new picture) if you want and tag the pelt different - but then you must also tag the items with the new tags ^^ sooo if you want this you can make a mode or change this manually in the item.json, in the constants.json and in the receipt - but i think at the moment its all ok - so wait and look what the devs make