Picture of O365 custom tile will not be displayed

Hi guys,

I need your help!

I created a custom tile within O365. Unfortunately the picture is not displayed. It is within a SharePoint document library and is shared with everyone. Furthermore, I tested it with the guest link and also with the link directly to the document. The file format is .png and 50x50 pixels.

What did I do wrong?

Any feedback is appreciated!

Thanks.

Julian