Is it possible to override the lightbox default vier with the fullscreen galleria plugin found here:http://wordpress.org/plugins/fullscreen-galleria/
this would make the images appear much nicer.
if so please can you tell me how
Yes, you can override default rtMedia lightbox by disabling lightbox from rtMedia admin settings and can bind whichever lightbox you want. You may need to check how this plugin bind lightbox with html elements to bind it with rtMedia media.