It is not clear what exactly the benefit will be except that spammy scraper sites have less useful content.
First of all, those sites don't care about the images, they are only interested in directing traffic to them by having a good SEO. Images are hardly attributing to that.
If you are going to block images from loading from non-stack-exchange sites you also block legitimate uses of the content which can't be the goal of this request.
On top of that the blocking software should be implemented by imgur, not by Stack Exchange.
I think scrapers like the one you found should be reported and all possible means should be employed to shut those sites down. Only blocking part of the content is not going to help much while it does hamper legit use of the content.