thieves like us said:unforunately for us case modders, many of the backs of the displays are marked with marker from a QC worker in the factory
you can try (very carefully) to use either some alcohol or goo-gone (a very, very small amount!!) on a cotton square or folded piece of paper towel to remove the marker. be very careful that you don't over saturate the cotton/paper towel too much. I actually ruined one upper display long ago when some alcohol wicked its way into the display through the flexible ribbon cable
I think I might have a better way around this issue. I am thinking of putting this behind the top screen and it would hopefully cover most or all of the writing.
(Warning My Little Pony image link.)
Rainbow Dash Papercraft.
Now, it would just be a standard printing paper in high the highest quality I can get out of my printer. Would the DS Lite be able to fit back together it the thickness of standard printer/copy paper? I figure this would be a good way to show off my liking for Rainbow Dash/MLP:FiM