Since we have decided that horizontal picture frames are a thing, could we have a relook at other concepts that are currently locked in a singular frame of reference?
1)portals. We currently have 3 portals: the entry portal to the End found in strongholds, the pill-shaped gateway portal leading to the gateway islands with end cities and chorus plants, and the nether portal. We technically cannot create either of the end portals outside of creative mode or commands, but it would be nice to be able to come up with different designs that we could still activate per normal or even use in conjunction with command blocks to create nifty non-portal concepts (ie, forcefields).
2)fence posts and/or gates. The change here would be to define orientation based on the blockface being clicked on...if you click on a top or bottom face the fence gets oriented vertically (like now) but if you click on a side face it gets oriented horizontally.