I had no idea where to put this, pardon me.
So I was trying to upload a background that was the exact needed size.
But then it told me “Images must be at least 640 wide and 1136 tall. Yours is only 1136x640!”
And I was like uM excuSe mE? O_o
I am NOT reversing the width and height, I need this as a three-panel background…
you can use this website http://www.simpleimageresizer.com/
It usually resizes the image and the image looks the same as the original
Thank you so much! I’ll try that 
Um… it squished my image 
But thanks anyway!
oh sorry usually for me it doesn’t squish it 
It needs to be bigger for 3 zones.
1280x1136
640x1136 is for 1 zone typically.
thank you so much!! This was super helpful 