To wear official rank insignia or unit patches is tolerated here but all in all a big no go because as soon as someone think you're on official duty, you may find yourself prosecuted for impersonating a public servant. In any case punishable by law is to use the official flag and that thing on the wall behind you on the picture second to the bottom is beyond all doubts an official state flag. Where have you got it from?
Compare:
That's the inofficial but tolerated
Bundesflagge, that shows the
Bundeswappen (Federal Coat of Arms) on three fesses of black, red and gold:
- ok
And that's the official state flag, the
Bundesdienstflagge, showing the
Bundesschild (Federal Crest) which must not be used neither by any authorities of the German states nor an individual:
- not okay
