I'd like to see more nice colorings for me metal parts of our guns. In fact I very like the chrome-like metal skin (in the free new year's pack) for the barrels so much, that I feel, I would buy a whole skin pack with skins focussed on barrel colorings (not spray or something... just dofferent types of metal, chrome etc.)
E.g. there is already a pink-ish chrome skin around. I wish for more of them. How awsome these shiny skins might look you already see on the .300 canning magnum with the chrome-copper skin that comes with gun by default.
I'd definetly spend some € on such skins.
Right now, skins in the "material" category, especially metals are just too few, even if you own all skin packs.