To be able to upload and change the Mosaic Logo:
Go to config tools.
Select Form/Letter templates.
Go to edit and existing form by clicking View template version on the far right.
Then edit template version.
Click template properties in the top left.
Go to the the printing properties tab.
Choose the image to upload and click confirm.
Leave without editing the form and the image will now be uploaded.
Go to system properties and find customerlogo.
Change the end of the below file path from servelechsc_letter_2017.jpg to the name of the image you uploaded file extension is required.
controller/templates/images?libraryBlobUserCode=servelechsc_letter_2017.jpg
11. Save and wait for mosaic to be restarted and it should display the new image once mosaic is back up and running.