I do like these ideas, and your kept to my preferred theme of nature. So, what your saying is, I could change the entire workd to look like it's been taken over by humans? With custom trees and all?
I am glad you like the ideas! I suggest you do what makes you feel most happy and inspired to work on! And I hope you want to share the results as you go along!
Creating custom trees can make a build very beautiful, but placing all 'by hand' requires a lot of patience. I think many people use an editor, such as WorldEdit for custom trees. They make a set of different trees to use as templates, and then copy and paste these out onto larger areas. There are also brush tools and others similar to image editing tools, but for 3D, to help create for example the first large 'ball' of the tree, so you don't need to place each leafblock one at a time. I don't know any more details, since I have never done it myself, but I am going to try it out in the coming week.
1) A tree village/city! It is very popular among fantasy artists, so there is plenty of reference material to look at online, in many styles.
2) Palace/temple gardens. With canals. waterfalls and structures they have the potential to look extraordinary. I think especially jungle/desert using any inspiration from many ancient Earth cultures (Aztecs, Incas, Babylonians. Greeks, Egyptians) lends itself very well to Minecraft, since they had quite square architecture. It makes it easier to replicate with blocks.
3) A small village centered around a certain activity. Can be cutting lumber and making things out of it. Mining. Fishing. Farming. Start with buildings needed to gather the raw material, and only add as much of the refinement process as you want! For example: Lumberjack huts, sawmill and shipdock to export the planks. Or wheat fields, farmer's huts, wind or water mill, then a donkey stall for export. And it is easy to expand if you come back to it later.
4) A group of animals which is not already in Minecraft, and adapting the environment for them. As an example, elephants or dinosaurs! But even building a special location for the ones in the game could be enough, for example caves where a pack of wolves live. Or a rabbit hill with a lot of tunnels.
My creative world has some builds which might fit as a starting point too:
- An amusement park/theme park. Could be made into more of a natural park?
- A self-sustainable/ecological village (modern, but produces its basic needs itself (energy/food/clothes/buildings)
- A hideout (for example for pirates/bandits/explorers/a primitive tribe/a dragon)