Hey @larry_barrett ,
thank you for your response. I found this: https://www.jamf.com/jamf-nation/feature-requests/8163/fix-the-self-service-header-image-scaling-and-specs
But my problem is, that I can upload and use some pictures as header, but not all. For example i could use the pic called "testheader.png" but not the "header4.png"
Is there a maximal size for the data-file (max 1000 KB, or something like that) ?