From a graphic design point of view, what would be a good way to let the viewer know, or better said, I want the user to "get it as he sees it" without further explanation that what I am showing is not the whole image, It is just a crop(ie. a small area of the whole image).
I need some examples.. advice, you can be broad... give examples from other fields.
I am attaching a screenshot of what I have so far, the way I did it is that I added a frame of the whole image, and then inside that frame there is this crop I was talking about.. But I am not so satisfied with the result, I am out of ideas. Any help is much appreciated.

Maybe this is a question for the UX site, but I have a feeling I might get better answers here. THANK YOU.