You can use any external oscillator you want, as long as you pre-scale it to 16 MHz. For example you could use a 64 MHz oscillator and a divide-by-4 external pre-scaler to feed 16 MHz to the ATmega.
You can use any external oscillator you want, as long as you pre-scale it to 16 MHz. For example you could use a 64 MHz oscillator and a divide-by-4 external pre-scaler to feed 16 MHz to the ATmega.