Moving some of the tumbr gallery I know would be rather subjective. However, the tumblr gallery has +5,800 images where as many of the other galleries I’d think they would fit better in are lucky if they have even 150 images. That exact Frozen example, while from tumblr, IMO would be better in the gallery documenting the spread of Frozen on the internet than documenting tumblr as a site. After all, though there is text beneath it, the text is pretty much still referring to Frozen. Meta images from tumblr (images from tumblr, about tumblr) I don’t think anyone would have issue with staying. Images about tumblr that may not be from tumblr are fine as well. Images without any commentary, with only being relevant to tumblr because “I saw it on tumblr” I think are pretty good to flag and change location if there is an existing entry. If its an image from tumblr with commentary and no existing gallery really suits it, I think it fine as is. After that though… it’s kinda hit and miss.
I personally might think this image suits the entry its in much better than tumblr, but others might not feel the same way (after all, the meme isn’t mentioned by name). However, it often feels like people just post things to the trending galleries for easy karma instead of contributing to parts of the site that could really use it more.
As for the question of: “if you have a reaction face that is of a dbz character, where does it go?” there’s the rub. I personally think that, since the Dragon Ball gallery has fewer than 300 images, versus the +21,000 images in the reaction faces gallery, it would do more good to have more examples in the Dragon Ball gallery (not to mention it is easier to see if it is a repost). Similarly, I think that a Crossover between Gurren Lagann and Mass Effect would do more good in either (or both) of those galleries than the alternative universe or crossover galleries.
Despite this, I even have differences of opinion on that. I know that there are a lot of examples of the special feeling meme (with ~300 images in the gallery right now), and a few of them are variants with Kantai Collection (right now 15 that gallery has images). However, as it is a specific meme, I think those variants (with tags) are better in the special feeling gallery.
Of course, all of this could be partially resolved by just reposting the same image in different (IMO more appropriate) galleries, but I feel kinda awkward farming KYM just to repost. I get a little bothered seeing other people do it, though I might not be so bothered if they would go ahead and copy the tags and the source along with the image. I also think it sorta encourages people to just post in the most popular galleries instead of adding more meaningful contributions.
However, having more people going out and adding appropriate tags is always a good thing, even if everything stays the same, so keep it up. I’ve added a huge number of tags to things this past week and know it can be a little unrewarding, but it makes it significantly easier to find things on the site.