I've just realised that if your in singleplayer (any time) you can press start > bonuses > unlocks
And you can purchase skins for your characters such as backpacks, shirts and J&D easter egg clothing in the bonuses menu you can also purchase concept art and render mode selct; black and white, dreampop and old west style renders!
Never knew about this so I assume that other members of the community might not realise this either! This is going to draw me into a 3rd playthrough eventually with some custom gear
ps. you unlock more items for completing hard/survival mode etc.