How do I hang individual handmade tiles on a painted wall? Tile mural...?

Assuming the tiles are relatively small and thin (i.e. not 12" square and 3/4" thick) most can hang from a ring or can tab glued to the back with epoxy or hot melt glue and hung on a small nail with the head sticking out of the wall. If there is a chance people will brush against them and knock them down, it would be better to use monofilament fishing line to hang them from points near the ceiling so if touched they just swing.

There are special kits that come with two pots - one is a special primer to give your tiles a 'key'. This means it takes the shiny layer off to make the top coat stick on properly. Your hardware store people should know about this kind of thing. Before you start, clean the tiles perfectly with sugar-soap, then wipe down with methylated spirits. Leave to dry, then follow the instructions on the new 2-pot paint kit properly. The problem with painted tiles is that the grout and the tiles will be the same colour. If you have patience and a steady hand, you can mark out the grout lines in white afterwards if you use coloured paint, or a slightly greyer paint if you use white for the tiles. I'm sure you know what I mean. I also left you a link for a spray-on product that comes up shiny, like tiles. Good luck