Just as the Nether and the Overworld have received more features, so to should the End dimension.
Here is a list of improvements which I think could be added:
More purpur blocks: If there exists a type of block which can be crafted from planks and/or sticks, there should be a purpur version, craftable from purpur and popped chorus fruit (I am thinking of purpur ladders, purpur doors, purpur buttons, purpur pressure plates, purpur fences, purpur fences/fencegates).
More endstone blocks: If there exists a block which can be crafted from cobblestone, there should be a matching end version, crafted from endstone (chiseled endstone, endstone slabs, endstone stairs, endstone buttons, endstone walls, smooth endstone (made by smelting regular endstone), smooth endstone blocks/slabs/stairs/buttons, cracked endstone bricks, etc.
Bigger outer end islands, with more content, namely ravines, caves, and dungeons.
End sand and end gravel. These anti-gravity blocks fall upwards if they don't have a solid block above them. They spawn on the undersides of most end islands.
A dragonslayer status effect, given to any player who kills, or helps kill, the end dragon. If you have it, you can trade with endermen. When you have enough money (popped chorus fruit) in your hand, endermen near you will appear to be holding blocks to trade to you. Right clicking on the enderman, or toss the money in the world, and the enderman will consume the money and place down his held block. Killing endermen, or changing dimensions, halves the duration of the status effect.
More native plantlife, such as end vines, mostly for decoration, but also for crafting e.g. mossy end brick.
The choice of what biome each part of the end could made with the aid of a formula similar to this one, which produces a spiral. At the same time, each newly spawned End Gateway structure (the ones made when the dragon is killed) is placed somewhere somewhere along this same spiral. Because a spiral has unlimited length, every time you kill a dragon, a new End Gateway structure spawns.
A new hostile mob, the enderslime. This black and purple cubic slime jumps much further than his overworld and nether cousins, enough to travel between end islands which aren't crazily far apart. He's almost as dumb as normal slimes, but if he's about jump towards a player who is moving, the enderslime will sometimes aim to intercept. The enderslime drops an enderslime pearl. When a player uses an enderslime pearl, it produces a projectile, similar to a snowball or enderpearl projectile, but black and purple. When this projectile hits a block or mob, it replaces itself with an ender pearl projectile, whose trajectory is basically a "bounce" of the enderslime projectile. This bounced enderpearl's "Owner" tag is the same as the player who threw the enderslime pearl.
Chorroded chest, crafted from one chest, four chorus fruit, four ender pearls. Whenever this hydrophobic chest gets wet, it teleports to a random nearby dry location, taking it's contents with it. It will also try to teleport if none of the 6 adjacent blocks are not solid. The range of it's teleportation is the same as a shulker.
Just as the Nether and the Overworld have received more features, so to should the End dimension.
Here is a list of improvements which I think could be added: