It can be inconsistent. The best results are when Save Thumbnail is used when the template is first saved. Don't forget that to save the thumbnail there must be changes to save in the document/template. This is most easily done by adding a character then backspacing to remove it.

Generating the thumbnail is the only way that you will get an image of your template in the Backstage view for File New.

If you unzip a template you will find the image in the docProps folder in either png or emf format. You can make one yourself by taking a screenshot of the first page in Print Preview.

Attached Images

Screenshot 2022-06-18 215251.png (24.3 KB, 16 views)