I decided to go for a 'day and night' theme in the case covering.

First I figured a line to split the colours for the case. I was a bit lazy here and just covered the case with one paper and then glued the other with paste glue on top. I used paste glue instead of PVA because when PVA dries, it leaves a glossy surface that would definitely show. Paste glue dries out matte though and left no stain whatsoever. I fixed the transparent paper with the design to the case, placed the foil beneath and started tracing with a foil pen and that is pretty much all there is to it.