I assumed that the German Empire and its paraphernalia would be verboten in the mindset of Germans.
Kaiserreich nostalgia seems to be at least tolerated amongt right-wingers like DDR nostalgia is in the far left. Although at least some symbols of the German Empire (such as the Black-Red-White flag) are used by Nazis to circumvent bans on swastikas.
You should visit my Grandmother's house
But honestly I don't see any stigma attached to artefacts from that era. Many of our most important streets and monuments are dedicated to key monarchists, with only minimal controversy.