Is there a way to customize the horizontal padding between an image and text in a Label widget when compound=left or right?
The 2 ways I can think of are:

Use PIL to dynamically add columns of pixels to an image
Insert or append spaces to the text= option of the label to force the separation of image and text

What I'm looking for is a way to specify the horizontal padding (between image and text) in pixels.
There is no built-in way to do what you want. Your own suggestions are good. Another option is to create a frame, and place separate image and label widgets in the frame. You then have complete control of the placement of the widgets
Python/Tkinter: Customize horizontal padding between image and text in Label widget?