I almost forgot about this... borrowed...

FREE TomTom GPS POIs, Colour Schemes, Voice, 3D Symbols (including Christmas Symbols)

This site is a good resource for free custom-made GPS car symbols, colour schemes, voice warning sounds and information alerts (amongst other things).

I keep it bookmarked to get the Christmas symbols for my TomTom every year, but there's also a lot of other good info on the site too.