How can I link to a local image from my home screen? We are able to create a link to a website and put this link on our Home screen by using the Add shortcut to home inside the browser's context menu.

I would like to do the same for an image that is local to my phone, so that I can click on the button and have that particular image display.

How might I achieve this?
There are actually many ways  to achieve the goal.
Method 1

Install ES File Explorer -- I'm suggesting it because  I know that it provides a file widget.
In your default launcher, go to Widgets → choose ES File Explorer → locate and select the image you want to be launched by the shortcut, and it would be placed on your home screen now.

Method 2
You already know it.
Open your browser, enter file:/// in the URL bar → locate to the folder where the image is located and then tap on it so that the browser should load it (show it, not download it) → use &quot;Add shortcut to home&quot; so that the shortcut can be created on the home screen.
Note that I tested this method on Firefox for Android and works well, but Chrome doesn't work.
Method 3
Find the activity responsible for showing the image in your default gallery app, input the data (image URI) into it, and use them in the Tasker to create a shortcut. (Use my answer for know-how.)