Since I've upgraded Balsa to 2.3.8 some of the toolbar button images have disappeared. Does anyone know where they are kept?

I can see some in /usr/share/balsa/hicolo/24x24/apps/ and I've added one called 'balsa-compose.png' which I obtained from a Balsa Theme but it doesn't show up.

One other puzzle is that there is a printer button with an image showing but it's not in the list in the above directory.