1, which means different:

Picture: image in a broad sense, which can refer to any picture, such as painting, artistic painting, etc.

Photo: refers to a photo, that is, the kind taken.

2. Different parts of speech:

Picture: you can be a transitive verb, and you can be "imaginary" like imagine;

Figure: There is only one part of speech: nouns.

3, the scope of use is different:

Pictures: can refer to photos or pictures published in newspapers, magazines, etc. Used as a verb.

A photo can only be regarded as an objective object.