Any image can be added to be used as the focal point image for the alternate colorways in the product popup.  Simply name the desired image to product number_colorcode_swatch.  This image will be used for the alternate colorway circles in the product pop up.

You should use your current naming convention (product/color/gender/etc) then append "_swatch"

We also support "-swatch" 

Recommended Image Specifications: 1500x1500 (Images can be the same size a normal images because they can be zoomed in on the product pop up)