To change login screen, you must change some files into OpenKM.war directory structure ( OpenKM.war is into OpenKM.ear ). The related login file is login.jsp int doc-root directory ( also in it file are main image files ).
Other change like colors etc... into OpenKM can made on css file styles.css at doc-root/es.git.openkm.frontend/ directory.
On next version probably we\'ll put OpenKM.ear exploded and some changes it\'ll be more easilly done than now ( opening and modifying .ear .war files ).