When viewing an image on a website, if you Open Image In A New Tab, it will often open, with a long URL, which finishes in a number and file type, like jpg etc, which tends to be the file details for the image, allocated by the smartphone or digital camera which took it.
Often people upload a number of images to a website, from which they select only one or two to display on the website, however the others are often left within the website & server.
By adjusting the number of the URL, going up and down the file number, you may locate other images in the sequence, which aren't displayed on the website.
So, in the below redacted example, the original image had a URL of
There used to be several useful add-ons & extensions to assist with this, however they were all withdrawn a number of years ago, so you mostly have to manually search, although there is a linked resource called Fuskrat on Github.