I need some advice

[bleakoptimism.livejournal.com]

First post, been reading and watching for a while, but inspiration time has come and I have embarked on a project that is a bit beyond my expertise, which has mainly been saeing and what not, I got a metal lunch case/tin for my friends birthday ebcause she really wants one, but I couldn't afford a fancy one from the itnernet, I found a cheapie disney one in a toy store that is perfect but I want to decorate it. The decorating bit is fine, I can think of pictures to stick on like a collage or even paint it, thing is I want to seal it so my work doesn't melt or run or come off when she uses it, it needs to be practical. That can I use to give it a shiny smooth hard coating that won't run in water or come to pieces. I thought of a varnish spray but I don't think they are water resistant enough or thick enough. Any suggestions? I checked the FAQ and back searched the latest entries and couldn't find anything and I would really appreciate the help