Shows with aesthetics I really, really like include:
Steven Universe
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Not only are the backgrounds really nice pastel palettes, but also the soundtrack has a really nice kind of minimalistic sound palette as well so everything looks and feels very nice and pretty and cohesive.
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Over the Garden Wall
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This is now my favorite thing to watch when it first starts feeling like Fall. The colors are all fall-y and the settings are all old timey and nostalgic and so is the soundtrack. Again, everything feels visually and audio-ly and thematically unified which really appeals to me.
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These are the top two that come to mind right now. I guess I really like it when the visuals in a show as well as the soundtrack feel really cohesive around a theme. Where it has a specific style that really fits with the mood of the show? That's not to say I don't love some shows that you can't really say the same about, just that this is definitely my favorite style in animation, even if not all of my favorite shows feature it.