Today I bring you several custom infinite flat worlds, very useful to create our maps. I'm sure more than one might interest you.
The following worlds are created with the help of MinecraftUniversalEditor program, customized by me and I have also added in a main chest some interesting items that could be useful for you. The items I added normally cannot be obtained in the inventory and can only be obtained with external commands or programs.

(Some worlds have their own biome)