You should have some of your teachat people send in some stuff...
As a musician by training (several 4-year degrees but not much to do with 'em!), I might have a bit of insight into this question, as it is one I've asked myself when envisioning my own tea shop. I like the idea of Jazz, but it would need to be jazz with a twist - some of Norah Jones' newer stuff would do, it's mellow but interesting.
I love the idea of mixing Jazz Noveau with ethnic sounds as well; you can get really good CDs of traditional Indian sitar stuff, Japanese Shakuhachi (blown flutes), and traditional Chinese music that is never boisterous or unexpected (like a lot of classical music would be). If you do want to go the classical route, some good light stuff to play would be Chopin's nocturnes, Bach's English and French suites, etc. I can give more suggestions if you'd like.