Acc to Mollo & Turner, he's a stormtrooper of das Königliche Preußische Infanterie-Regt. Graf Barfuss (4.Westfalen) Nr.17 . Some googling turns up this.
They say photo is from Spring 1918, in Champagne. Could Wikipedia be wrong?
That's all I got, but it might lead somewhere.
Talking of iconic images, it reminds me that there was a TV doco about attempts to identify the British soldier in the often-shown clip in which he's carrying a wounded man across his shoulders. Acc to this there is a possible i.d., although I thought I remembered the doco saying that they drew a blank.
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"Sometimes things that are not true are included in Wikipedia. While at first glance that may appear like a very great problem for Wikipedia, in reality is it not. In fact, it's a good thing." - Wikipedia.