So the KYM database's glorious image gallery.. But i don't really understand what exactly decides suggestions..
You'll say "course cause of tagging" maybe. Well your answer is true, because if you don't tag anything to your picture, you won't get any suggestion. Oh wait. It only valid in profile uploads. It may also depends on upvote or popularity.
But here is a KYM in a nutshell. Popular tags like "gif" always show popular ones from gifs like that "Potter shooting Voldemort". It always suggests the same things over and over.
Lets take a look at the images which don't have any kind of tag. Here, here also here.
As you see. Every low rated "reaction faces" images have same suggestions.
Asking again:
What the hell decides the suggestions? Will tagging show us something different from ponies, the things that already have been shown a millions of times or unrelated stuff?