What is a picture within a picture called?

Answer 1

Its called a picture within a picture

The term is inset.

A picture that has a smaller copy of itself within the picture, with the copy having an even smaller copy, that continues to (theoretically) infinity, is called a Droste Effect or recursive picture.

Answer 2

If it's a picture of the same picture then it's known as the Droste effect. But a more generic for this is just a recursive picture.

Answer 3

Wla