I'm back.
I ended up finding the plugin. It is in fact the Battle Core.
Viewing post in Issue in Battle Screen
See if there is any configuration on the battle core that changes how the SV Battlers work, and try to disable, so they can behave as default. Because I know these visu plugins have a LOT of features. If still that do not solve the problem. I may take a look to see if I find a solution. But the chances are very tiny with a plugin of the size of the Battle Core and also obfuscated =/
They are incompatible then. If you say you checked every plugin parameter and they do not have any option that can disable the changes on the battler image... Since Visustella plugin is obfuscated, there is nothing else I can do. The solution would be me look at both codes and make an exception so the Visustella plugin does not mess with the battler image/code logic. But, I can't see the code...