Thanks to Dave Granholm, i got to know of a way to hide the Banner in Dashboards using GO URL. It is very strange that this is not documented in the current version though this was available in the Siebel Analytics 7.5 user guide.
Sample GO URL:
http://localhost:9704/analytics/saw.dll?PortalPages&PortalPath=/shared/Paint%20Demo/_portal/&Page=Brand+Analysis&Syndicate=siebel&nquser=Administrator&nqpassword=Administrator
As you see above following are the parameters
1. PortalPath - Direct path to the Dashboards.
2. Page - This points to the page within the dashboard
3. Syndicate=siebel - This is required for the GO URL to work. I think this is how the dashboards are integrated into Siebel CRM.
4. nquser - Username
5. nqpassword - Password
But if you want more customizations the only way is to create custom styles and skins. Lets test out the above GO URL.
http://localhost:9704/analytics/saw.dll?PortalPages&PortalPath=/shared/Paint%20Demo/_portal/&Page=Brand+Analysis&Syndicate=siebel&nquser=Administrator&nqpassword=Administrator
http://localhost:9704/analytics/saw.dll?PortalPages&PortalPath=/shared/Paint%20Demo/_portal/&Page=Regional+Analysis&Syndicate=siebel&nquser=Administrator&nqpassword=Administrator