Custom icons in ActionBar.
You have to invoke somewhere in code method Base_ActionBarCommon::add
As first parameter you should put predefined icon name from modules/ActionBar/theme/icons without extension - e.g. Base_ActionBarCommon::add('save', ...)
or relative icon url like 'modules/Custom/MyModule/icon.png'.
Custom column in RB - use calculated field with defined display callback. And enable option 'visible' to show in column view.
Regards,
Adam