Hey Cherylyn, I've been browsing the Osprey books the last few evenings, and I found 4 images that you may find useful. Two of which are modern artwork (by Graham Turner). One is an oil painting and two are woodcuts. Here you go...

This has a gunner showing the cartridges on his back. This is taken from the Osprey Pavia 1525 book, page 42

This has 2 gunners with their cartridges handing from the skinny strap. Taken from the same Osprey Pavia 1525 book, page 66.

This is a nice oil painting that shows the guy who’s slightly blurry on the far left has a dark strap with cartridges hanging across his chest. Also, the soldier second from the right has a strap across his shoulders with cartridges hanging. Oh yeah, taken from same Osprey book Pavia 1525, page 19

This has the front soldier showing off his back and you can see the strap with cartridges hanging there. Also, check out the second guy, he’s got a nice powder flask like yours and Chris’s flasks! Taken from Triumph of Maximilian in the Osprey book Armies of the German Peasants’ War 1524-26, page 33

This is a studly soldier! Anyways, check out his nice powder flask and those sexy cartridges hanging on the strap around his neck. Taken from Triumph of Maximilian in the Osprey book Armies of the German Peasants’ War 1524-26, page 33

Anyways, there you go! If I find more, I will post them for you as well!
xoxo