Word for a single picture which can be interpreted in two different ways

Solution 1:

Similar to @Lawrence's answer but with little more context.

As per Wikipedia, your picture is an optical illusion, and within the set of optical illusions, a cognitive illusion, and within the set of cognitive illusions, an ambiguous illusion.

Ambiguous illusions are pictures or objects that elicit a perceptual "switch" between the alternative interpretations. The Necker cube is a well-known example; other instances are the Rubin vase and the "squircle", based on Kokichi Sugihara's ambiguous cylinder illusion.

Solution 2:

They are called ambiguous images. One can argue that there is ambiguity in what the image ‘should’ be, though that ambiguity is often intentional.

Ambiguous images or reversible figures are visual forms which exploit graphical similarities and other properties of visual system interpretation between two or more distinct image forms. These are famous for inducing the phenomenon of multistable perception. -Wikipedia