Activello Slider: Optimal Image Size

Hey, thanks for making amazing themes (I’m using illdy on another site – loving both), but I was wondering what image size is optimal to use with the slider? I have been using 1600×800 but lately it’s been cropping unexpectedly. Do you have a suggestion for the optimum size image to use to keep it from cropping important things out. Or, what would be ultimately superb, is there any way to adjust what area of the photo the slider shows??
Thanks so much,
LL
Laleelifestyle.com