Marinelli and Domain Access

New to Drupal and love the Marinrlli theme. I use Domain Access 7.x-3.8 with Marinelli on my main domain and a Marinelli sub theme on all the other domains. When I upload a new banner, banner is saved in public://banner/ and shows on all domains. Would like to see some added banner config on theme settings to change banner upload folder for each different sub theme. I have added form elements to theme settings (example on file attachment) but not sure about how to get the code to work right. Not sure if this is possible or not, but any help or if anyone can point me in the right direction would be appreciated.