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This is a very difficult question to answer. What appeals to some, doesn't appeal to others, so I can only give you a personal favourite of mine. This is a x64 texturepack and also is available with a version which includes many mods as well. It's called Soartex Fanver and can be found here, along with an alternative called Invictus :

https://soartex.net/downloads/

versions with included mod sprites can be found here :

https://soartex.net/downloads/modpacks/

Just browse through https://www.planetminecraft.com/resources/texture_packs/ there are lots of good ones there. You would have to be more specific if you want someone to suggest though. Default look, sci-fi look, etc.