Since I created my USB to have the persistence function, the customization was a piece of cake. The USB remebers all the settings for you.
I did go to settings, changed the wallpaper, added an international keyboard (good for those of you, who are bi/multi-lingual), adjusted what I want in the dock and status bar and ran updates.
That way, every time I start my Linux USB with Persistence, it's always ready to go and the same on any computer I use! :-)