For the sake of balance and impartiality
Lets see what the folks at SE meta, who disagreed with the edit, had to say
- Adding images to a question, that were not provided by the author, isn't an edit that will be approved. Both reasons are legitimate reasons to not approve your edit— Ramhound
- @Catija The only exception to their total control over the actual content is that they can't vandalize their own post. Yes, editing is part of the moderation of the site but it doesn't remove ownership from the author of the post. It is still their post, that they own. Edits are there to improve the presentation of posts and help the original author's content be better understood by others, not to change that content — Servy
- @Servy but we're not arguing different things, we just think about it in slightly different ways. This edit did "improve the presentation of the post and help the original author's content be better understood"... which is what I was saying. – Catija
- @Catija So then say that, because you didn't say that. Rather than saying the author of the post can't object you you changing the content of the post, say that this edit doesn't change the content of the post. Don't say that the author doesn't own the post when they unambiguously own the post, as is specifically laid out in the terms of service. – Servy
- @JamesWebster And you're welcome to act as if you don't own your own posts. You're even welcome to legally give up your own ownership rights for your own posts and put them into the public domain. What you aren't allowed to do is act as if anyone else doesn't own their own posts, because they do.
and this answer by a user with 52k which earned five upvotes but eight downvotes
Edits, especially suggested edits, are for improving the format of a post, not the content. Say somebody tried to do a numbered list but it didn't work, or they had a giant wall of text and it should be split into paragraphs. Fixing spelling mistakes and grammar issues are also in the realm of suggested edit work. But fixing content is not. The first comment is generated when people reject your edit for this reason. You tried to change the content. Don't do that.
The second comment is from someone who believes (it's not site policy) that if you commented on the post offering to edit in some relevant content, and the post owner commented say "sure, thanks" that the edit would be approved. They aren't necessarily correct, because edit-reviewers don't always read comments, but I suppose anything can happen.
Learn the difference between the two kinds of improving and you'll be less frustrated by the suggested edit process. For content improvement, if it's so minor that you don't think an answer of your own is warranted, this is a great use for comments. I often edit my own answers after people leave extra information in comments. @Kate Gregory
Now, let's see the minor edit that was approved. And yes, I am hung up on the term "minor" because it is misleading.

The owner of the post accepted the edit, so everyone's happy. We can agree that the edit was not harmful, but I never said it was. We can agree that the images are relevant, but if the previous suggested edit had included a link, I most probably would have looked at the source and then have made a different decision. Please note that the editor added the source in a second and final edit.
If a similar edit as the one proposed above was submitted for approval, I'm not sure I would have approved. It is a substantial edit, there's enough new content to post it as a separate answer. A good third answer is preferable in my eyes than a well-meaning edit. That is my opinion.
The users on SE meta, and here on ELL believe I lack experience when it comes to approving helpful edits. Nothing is further from the truth. These are my statistics for Suggested Edits review on EL&U https://english.stackexchange.com/review/suggested-edits/stats

Need I ask permission to edit an answer to add a minor improvement?