No idea if this will appeal to people, but it was driving me insane :( I was sick of having to zoom in all the time. Small thing, but it still got to me.
If any of you know how to use GreaseMonkey for Firefox or TaperMonkey for chrome then installing this would be a doodle and if you like bigger images it's good for you
Click the image and it'll be bigger.
https://greasyfork.org/en/scripts/8696-fix-games-workshop-image-viewer