To reproduce:

1. Place an item frame on the floor, or on the ceiling.
2. Place any block in the frame.

----> Observe that:

For ceiling frames:

• The bottom face of the item is lit up, even though it should be in shadow.
• One of the side faces is brighter than the rest, which is also incorrect.

For ground frames:

• The top face of the item is darkened, even though it should be lit up.
• One of the side faces is brighter than the rest, which is also incorrect.

This is most likely caused by the game rendering the item's lighting in the item frame as if it was horizontally positioned, while it isn't.

Notes:

This does NOT only occur when you rotate the item, as I know the shading doesn't change on horizontal item frames when they are rotated.

This is completely different, and affects the item when the frame is in default rotation.