Recently i was able to override the logo on the login page as you can see here >
<div class="logo"> <a href="/openmrs-standalone/referenceapplication/home.page"> <img src="/openmrs-standalone/ms/uiframework/resource/referenceapplication/images/openMrsLogo.png"> </a> </div> </header>
screen shot here
On the login.htm page you can override this openMrsLogo.png manually through referenceapplication module. then on the homepage like the screenshot @prapakaran provided, you can do this in uicommons under same folder. it seems to be little a bit hacky but it works, however am thrilled with https://github.com/fortitudoinc/openmrs-branding provided by @levine, it seems interesting am going to try running them module