Germans had a wide issue of pistols, steyr, frommel, FN, VIS, Walter. If I remember right they even issued Norwegian made 45 cal. Colts. So the Guns seen on photos might not been "captured" items.
I have yet not seen any photos of Germans carrying Garands or other US equiptment. I think the reason of this was that when ever Germans encountered US forces they retreated (except during the Ardenner ´44).
I know that the English stengun was popular and was later in the war, copied. There was also a exact replica of the Sten made for the German resistans "werewolfs".
The Soviet ppsh was even rechambered by the Germans to 9mm para. and reissued to easternfront. Though the 7,63 soviet is a very, very nice round, very fast and accurate (.30 mauser).
I have a SIG 210 chambered for this round (.30 mauser) and it is extreamly accurate.