How to change Excel 2013 Template Miniature

Question

Is there a simple way to change / replace the automatically generated Template Miniature with a different image.

Answer 1

I have checked this out for Excel 2016 but the process is similar.

First, the thumbnail is generated and part of the file. There is no official process. A description for brave Office pros is shown below.

---

You can do this:

First, close Excel!

1. Get to the location of your template
2. Make a copy
3. Rename the file extension to .zip
4. Unzip the file into a new folder using the Windows Zip utility
5. Search the tree of files for a file called thumbnail.wmf
6. Open PowerPoint and create an empty presentation
7. Use the function "Insert an Image" and add the thumbnail.wmf to the slide
8. Remove everything else from the slide
9. Try to ungroup - it fails with a message asking to convert to a drawing object

From here you have two options. Either convert, ungroup, change and proceed or throw away and create a new image from scratch.

10. Work on image and group your image (the old or a new one), then
11. Right click on the grouped image and click "Save as picture"
12. Choose the filetype "wmf" and name it the same as before and overwrite the existing thumbnail.wmf
13. Go INTO the folder using Windows Explorer of unpacked files, hit Ctrl-A (Select All)
14. Right click and say "Send to" --> "Compressed (zipped) folder". Give it a new name.
15. Hit F2 to rename the file
16. Remove the file extension .zip

Now, open Excel!

Hit "New", "Personal" and you see your template with your custom image in full width and height. Repeat steps 10 to 16 until you're satisfied.

---

Drawbacks: Once you edit your file in excel and save as template with thumbnails option (advanced properties) switched on, Excel will overwrite your custom wmf-file. You have to repeat the steps "Unpack -> Replace File -> Pack" every time.

I'll post an update once I found a better solution.

Answer 2

Here is an automation of the process that might help with understanding the process described in the answer.

Python 3 code snippet

import zipfile
import shutil

exfilename = 'MYTEMPLATE.xltm'
a_path='C:\\TEMP'
th_path='mythumbnail.wmf'

with zipfile.ZipFile (exfilename, 'r') as zf:

    #Extract to temporary folder
    zf.extractall(a_path)

    #replace the thumbnail
    shutil.copyfile(th_path,a_path+'\\docProps\\thumbnail.wmf')

    #remake the zip as a new file
    shutil.make_archive('TEMP_ARCHIVE','zip',a_path)

    #rename back to original, replacing original
    shutil.move('TEMP_ARCHIVE.zip',exfilename)

    #clean-up temporary files
    shutil.rmtree(a_path)