We designed our own set of images. We, then, replaced those present in /webapp/media/images/ with our own. See screenshots below
/webapp/media/portlet.css: customized portlet.css
/webapp/media/commons.css: customized commons.css
/webapp/media/helpdesk.css: customized helpdesk.css
/properties/domain/email.css: customized email.css
– more coming soon –