While I would love having full Layer support with nesting and grouping and all of that jazz, a simple, whiteboard-based paradigm might be an 80/20 solution for how I’d use layers. Give us two layers for a board “Surface” (the bottom layer) and “Items” (the top layer).
Most of the time, what I’m doing is trying to separate things that would be the equivalent of the “surface” of the whiteboard (labels, shapes, areas, and images that I don’t expect to move), and things that are “items” on the whiteboard (sticky notes, cards, some images, that I DO expect to move around etc.).
Working in one of the two layers would be like a Mode - CURRENTLY EDITING SURFACE or CURRENTLY EDITING ITEMS. Switching to edit one of those layers would lock the other layer, so if I am in the Items layer, I can’t do anything to the surface, it functions as a background image, and if I’m editing the surface, the items are all locked and I can’t do anything with them.
Combining this with my other request today, https://community.miro.com/wish-list-32/usage-rights-for-facilitators-vs-participants-440, facilitators could be given access to edit the surface where participants would only have access to the Items layer.