Can you change the web page title of the login screen from "Login - Splunk" to something else?
I have tried editing the login.html page but this only allows you to change the word "Login", the "- Splunk" part appears hard-coded although I can't find where this is specified.
if you edit your javascript that fires while loading the page you can add your own title
document.title = "My title";
Have a look at $SPLUNKHOME/share/splunk/search_mrsparkle/templates/layout/base.html lines 90 following and the other template files.
I'm not sure where that setting is found, but according to http://www.splunk.com/view/SP-CAAAFT9, you should probably not remove "Splunk". It probably violates a TOS somewhere as well.