ImageQ

ImageQ[image] yields True if image has the form of a valid Image or Image3D object, and False otherwise.

Examples

Test for valid image:

ImageQ[ExampleData[{"TestImage", "Lena"}]]
(* True *)

Non-image returns False:

ImageQ[{1, 2, 3}]
(* False *)

Please visit the official Wolfram Language Reference for more details.