A lot of people in the Minecraft community love Minecraft's terrain generation. You can see tons of posts on reddit giving ideas to improve terrain generation: add more biomes, improve the ones that exist, and add more terrain features. While a mod like that is being developed, it's still far off from release. Until then, many users are turning to custom terrain maps. However, none of those were big enough for servers, or contained many biomes, but were actually just a small area that you could (with a lot of MCEdit knowledge) add into your own world. Now, Aurelien_Sama, a map creator that had previously come out with cool maps, released his latest work, and it's truly beautiful.
It includes 3 biomes/regions, each very radically different from each other. First off we have Haschia - this is a normal forest biome, but with giant overhangs, river canyons, waterfalls, high mountains and low valleys. Part of it is from Aurelien_Sama's previous map of the same name, with the other custom built part added. It's beautiful in it's own right, and is a wonderful landscape to look at. You spawn in this region, in a big valley where you could build your base/city.
Then we have the snow biome, I like to call it Skyrim, which isn't your normal snow area. While Minecraft generates a barren, flat, wasteland, this is a mountainous area with only a couple of valleys, and the snow height actually increases with height, so mountain tops have full blocks on them, while valleys are just covered in a layer of snow. There are frozen rivers that cut between some mountains to make beautiful sights.
The desert biome also isn't just a desert. Aurelien_Sama put in a lot of work into making dunes, so it looks more realistic. There is a giant oasis in the middle, which… well just look at the featured image.
It's a very dynamic desert, and it's easy to get lost within, just like a desert should be.
A famous youtuber, Variede, actually made a video showcasing the map with a very vibrant biome-color setting:
The map has all of the underground features of regular Minecraft - caves, ores, mineshafts and dungeons. There is an End portal hidden somewhere. I haven't found it yet, and I've been using the map on my server for a week now.
I recommend you get this map. It's a very fun place to explore and build in. Get it here.