[2020] The 2020 Road Map is cool and all but shouldn't we know about this "Vanity" update for backpacks?

Echoing what u/Valseek said here:

• First, we're adjusting backpacks so that different versions you've picked up as quest/event rewards or from the Atomic Shop can be applied as skins.
• This will work similarly to how weapon and armor skins do now. You just need to add the new backpack appearance using the workbench modify menu, rather than crafting a whole new backpack every time.
• Second, the small backpack will also benefit from this change. So, you will be able to change its appearance as well using the different backpack skins you've unlocked.

Once we release patch 19, you'll be able to apply skins to new backpacks you craft, as well as the ones you already had in your inventory before the patch.