There is non.
As a 2D polygon shape it is an 8 sided octagon.
The equivalent of a octahedron as a 2D shape is an 8 sided octagon.
An octahedron is a 3D shape with 8 sides.
A camera is a 3D shape. A photograph is a 2D projection of a 3D shape onto a 2D shape.
An eight-faced 3D shape is called an octahedron. Any 3D shape (polyhedron) ends in -hedron, just like any 2D shape (polygon) ends in -gon, and octa- means 8.
It's a 2D shape.
A television set is a 3D shape. The image (picture) on the television screen is a 2D shape. 3D is when it has length, width, and height. 2D is only length and width.