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.
The problem was that these impressive helmets weren't well  suited for combat. Often they were made from leather with metal  added only as a decoration. They didn't cover much of the head either  and they were heavy. It's fairly evident that they were designed mostly  as a fashion statement, when you consider that cloth covers for the  helmets became standard issue in 1892. Why? Well, to protect them from  dirt - and also because the highly reflective nature of the helmets made  the soldiers wearing them very easy to spot.
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.