I would like to know if there is a way to choose which image shows as the main image for each section (when on the homepage under "Collections"). It's frustrating because sometimes I put the same design on a bunch of different products, and then on the home page it doesn't look good because you see the same image on a bunch of different things and it doesn't show that you have so many other options...Plus, one image might look better as the main image for canvas prints while a different image would be better for phone cases, and so on.
If anyone has input on this please let me know.
If I'm understanding this correctly, you want to change the order of your main pictures on each listing? You can only do that via the Etsy Seller Dashboard, not the Pattern Dashboard. The order of listings that appear on the website is the latest item you either posted, re-listed or sold. I don't know how you can change that order.
As @stufforama said, the items that show as the images for the Collections appear to be the most recently listed (whether added or sold). I don't even play with custom sorting on the Etsy page, so I don't know if it would have any effect on your Pattern site, but you could try it and find out.