If you drag the photos on your recipe will it stay in that order? I tried and had to submit it, and now it says it is up, but the photo didn't move to the order I dragged it. I just tried again, so is pending again - but maybe that is in vain.
I'm not 100% sure Maito but I don't think you can change the order the photos show on your recipes once you have already uploaded them. The photos show in the order they are uploaded.
If you post this in the help and suggestions forum admin will answer your question properly, they don't visit this forum often ;)
When you are editing the recipe, hover your mouse over the picture you want to be the default. The words will appear in the right hand top corner of the pick, default or Zoom. Click on use as default and that will the first pic to show up.