Which things should I have in mind when choosing LED backlight frequency in range 10 kHz to 100 kHz?
So are there any other important factors, other than EMI concerns, which need to be taken into account when selecting the PWM frequency?


Yes.

The higher the switching frequency, the more you have to charge / discharge whatever MOSFET that is being used for switching. So the larger input capacitance it has the more important it is. You're effectively just throwing away charges.

Transistors got rise time and fall time that are both above 0 seconds (not instant). This means that as a transistor is transitioning from conducting to not conducting, it will for a short moment have a high current and a high voltage across it. The higher the frequency the more often those high power losses happen.

Audible noise, I advice you strongly to use a PWM frequency of at least 40 kHz, this way you won't hear the switching and neither will your dogs or cats.