In 4.2 and when FioriLaunchad was launched, there also was a ThemeDesigner that you could install. There you could do some customization of the FioriLaunchpad, regarding to LOGOS, Backgrounds etc.
Yes, I’ve used it with a couple of clients. I believe the tool is in the Addons folder in the install. You have to copy the .war file to the Tomcat webapps folder, stop Tomcat, and start it again to get it to deploy so that you can use it.
Just to add, since I am working with custom themes right now.
The BusObjects theme designer is very limited, typically you will end up with having to identify the CSS elements (dev tool in your web browser) and then setting the properties in the css file :-/
Also, keep in mind, if you decide to use a custom theme there can only be ONE theme then, not multiple custom themes, a severe short coming iMHO