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Sorry that I am not familiar with Python, so I'm not sure if this is a correct fix. At least this works for me, I guess. The problem is that I want to put images on headers, some because then it could be put on the center of the slide, and some because I just want an image on a header. I found that headers are skipped to be processed by macros, so that images on headers aren't embedded. I am not sure if this is designed to work this way, but it works for me... :) Thank you for reading and considering!