Image occlusion was pioneered by Anki users in the medical community. Instead of typing "What is the femoral artery?" you upload a diagram of the leg and mask the femoral artery — the card shows the masked image and asks you to recall what's underneath.
It's more efficient than text cards for visual subjects because it preserves spatial context — you learn the location and the name simultaneously.
QuickCards has a built-in image occlusion editor: upload an image, drag boxes over the regions you want to hide, and save. AI-suggested masks are also available — paste a labeled diagram and the AI proposes occlusion regions automatically.