This means that when you save the block, you can save it as chest, furnace, crafting table, hopper, redstone, etc. It's basically an extension of the Ladder, Glowing, and Seat options that you currently have. This can also be extended into items. For example, pickaxes, axes, shovels, hoes, clocks, compasses, maps, etc. I understand that this might be difficult to implement, but it would increase the customization possibilities by a lot, and the entire premise of the mod is basically: More customizability for armor, tools, and blocks.

Added block inventory skin option in c86a778

Other options will be added in time