According to the Arteria plates there was a Slavonisch-Croatisches Freikorps which would imho would give some more colour to my Austrian revoluionionary 28mm army. Underneath some pictures; the first one of course of the Arteria plate.
I tried to find some suitable figures and found the Wagames Foundry Russian Pandour characters which led me to this wagames unit which are close enough for my to add to my FR Austrian army.