I thought I did it correctly, however the new feed doesn't show.

I think it's because I need to address the state, as the one below (without a list) functions correctly:

CameraPop.GetItem("camera_big").GetState(0).Image=urlPrefix+cameras[(item*2)+subitem-1];

Edit: fixed. I was addressing the dummy beneath the feed apparently as the feed was passthrough I didn't get the correct item index'