Skins for other things...

Why has riot never released like skins for the maps? Like Seasonal SR maps (like the harrowing or snowdown ones they said would make a return) or past season's maps, or that sort of thing? Or skins for the HUD/ablitity to mod it yourself, to make it easier for streamers or people who want to personalize it a bit but are worried about the terms? Or like skins for the client or ability to choose from past login screens?

I know the first would be mountains of work (and would probably cause each map skin to cost more than people would be willing to pay making it pointless) but i'm sure the latter wouldn't be so.