You don’t need to use a cartoonish image as I have done in this post, for this example. Any image will do; it can be a realistic image. I worked on the following image at 72 ppi (pixels per inch, RGB mode).
You will need to have whatever image you want to use cut out from the background for this to work.
The end result should look something like this shark image below – a halftone pattern around or behind the shape: