Suggestions for 24V white led light

Assuming you've used the right Vf and LED current in your calcs, this circuit will work - the rest depends on your definition of "background ambience lighting" and "reasonable".

If you have the parts, why not do the experiment and come back and tell US how well it works? :-)

Good Luck! Rich

Thanks, I'm building it this weekend.... I'll report back.

Works just fine, with very little difference in illumination from 21 to 27 volts. Total current @24V is 110mA.