Have you heard of speckle paint? these are the best things for cases.
then use a dremel tool to cut out a happy face. and insert a black light inside the case using a 5 1/2" drive bay fanbus switch to control the lights (go from white, to yello, to blue)
Once again, I reccomend speckle paint. It'll make the worst looking cases look awesome. Spray paint isn't too bad either. $3 for a can and spray the case in a well ventilated area.
Being creative <-- the best case you can possibly get.