Eric, further to the problem of incomplete URLs, I've checked back with old (2011 & 2012) CSV's from Things From Another World merchant. They used to have their images available through their affiliate image subdomain, eg. http://affimg.tfaw.com/covers/100/16/16577.jpg
Apparently, as their online business has gone from strength to strength, they serve them up through Amazon's Cloudfront service for speed of delivery etc.
Maybe it's unreasonable to ask you to implement an auto search/replace routine within DFR to add "http:" to the front of their datafile's image & thumbnail URLs. Maybe not.
Possibly it's an oversight by their web team when exporting the datafile to Shareasale.
So I'll get onto them today & see if anything can be done at their end to correct this feed glitch — if that's okay with you?