In the inventory, some blocks are lit from the top left side and some from the top right.

Left-lit blocks include:

• chests (plain, ender, trapped)
• fences and walls
• stairs
• mob heads (except player and zombie heads, which are completely black)
• beds
• shulker boxes

Also, item sprites and GUI elements are still shaded as if lit from the left side.

Everything else is lit from the right.