I've seen that one before, interesting picture. Gag or not, the SMLE's were probably issue weapons for them. There is one 'LK5' marked SMLE attested, and no doubt very many were seized after British and Dominion reverses at Dunkirk, across France, Greece, Crete, et al. Like other Beutewaffen, they probably went to second and third tier units, a number of which would be comprised of Luftwaffe ground personnel like the ones shown in the picture.
Thanks for posting these pics, especially the ones from the Police units in Yugoslavia. It's very interesting to see the M41 Carcanos in field use with Wehrmacht units!
Pat