The image selection question type allows for star rating and multiple choice selection, but no direct way to allow for image ranking. I think it would be as simple as asking the user to click the top ranked photo then gray out each photo as it's chosen until there's only one photo left. Just add "ranking" to that drop down menu that contains "star rating" and the multiple choice options in the image selection question panel.

Note: Image ranking is the primary question type used by pickfu.com -- and it's very helpful there.

I am aware of one workaround with answer piping, but it is extremely buggy (i.e. ask to select the top ranked photo through multiple successive multiple choice questions then pipe in the not chosen answers as the questions progress). I'll create a separate bug report for this other issue.