since rev865 marlin use symbolic icons for its toolbar.
If the button show a no entry symbol it means the icon theme you're using doesn't provide the requested icon.
Hopefully most theme fallback on gnome icons.
So intalling gnome-icon-theme-symbolic package should solve your issues.
I'll add the package to Marlin dependencies.
since rev865 marlin use symbolic icons for its toolbar.
If the button show a no entry symbol it means the icon theme you're using doesn't provide the requested icon.
Hopefully most theme fallback on gnome icons.
So intalling gnome-icon- theme-symbolic package should solve your issues.
I'll add the package to Marlin dependencies.