What I would love for them to add six different shades to each accent color, from light to dark, a la the little color bar in paint. That would give more options and making the phone more customizable. Plus they should throw in the high contrast as a regular style theme or a colorless/glass theme a la simple calendar...
I could have sworn it's yellowLets shake things up...
My favorite is brown. I switch the light and dark theme almost weekly and brown looks great with both.
Dark theme with cyan....i just do it because its the only colour it fits with my cyan 520 heheh