The bug

When placing a painting, it checks for intersections with other paintings and most blocks, but does not check for intersections with item frames. As a result, they can overlap, which causes heavy z-fighting.

How to reproduce

1. Build a wall
2. Place an item frame on the wall
3. Place a painting to the left of it
→ Overlap

Expected result
Painting treats item frame the same as another 1x1 painting, and will choose a size such that the occupied block is not overlapped.