Here's a great real-photo card of German soldiers wearing the Pickelhaube. That's the name of those ornate spiked helmets worn by Prussians and then other German military in the 19th and early 20th century. For formal occasions, various plumes could be attached to the finial to create an impressive ceremonial appearance.
Later, when World War I broke out, it was quickly discovered that the helmets were a serious liability for trench warfare. They didn't protect the wearer from shrapnel - and I'm sure you can just picture a line of the spikes sticking up from a foxhole. This lack of utility led to their replacement by unattractive steel helmets.
This card was sent in 1912 by Ulrich Baumann (?), who may well be one of the soldiers pictured on the front of the card. He sent the birthday greeting to Miss von Lorenz, who was staying with her excellency, Frau von Hugo, the wife of Major von Hugo, the German Military Attaché to Paris. It was sent to Pomerania, which was probably a vacation destination rather than their year-round residence. The postmark indicates that the card was sent from the Elsenborn Übungsplatz, a military training facility. Click here to see another card sent to Frau von Hugo.