According to the documentation, it states that I cannot use tiles to create object templates. So, how should I use an image as a template? I’m unsure how to add an image object from anywhere other than the tileset.
Where did you read that? You can create templates from Tile Objects just like any other object. Perhaps you misread the note about not being able to create templates from Tile Objects that use tiles from embedded tilesets?
I’ve identified the root cause of the issue. Instead of exporting the tileset, I was using an embedded tileset.