We all know from the sources that tell us that the Germanic tribes (as well as other barbarian peoples in the north like Celts and Slavs) had elaborate and colorful shield patterns, in order to display their tribal allegiance, rank, or family, or perhaps all three in one.
Unfortunately the reality is that most of these shields are lost because they were made of wood for most of history, and by the time metal shields became common among the Germanic tribes they were becoming increasingly Christian (however do not dismiss that medieval coat of arms and old tribal shield patterns may have a connection)
However we do have a few sources to run off of and one of them I found was an old Roman book that contains pictures of shield patterns used by a Roman mercenary unit of Germans, composed of several different tribes. Each tribal unit has its own shield design that bear great resemblance to the patterns used by the other tribes.