Ok, got it to work. but now, the model isnt working. It's my first time with models. but not with textures
You can copy the models from the respective version jar file.
You can find teh .jar file of your version going to .minecraft>versions>[Version/profile name]>.jar (open with winrar or 7zip)>assets>minecraft>blockstates/models (you need copy the files from both folders.
Remember to edit the modelswith a text editor to make it work if the name of the texture is different in yours.I recommend Notepad++
Edit:Also,the blcokstates may need to be edited if you make random textures.
The idea is interesting,but why the desert? I know we need more life on the game,but desert already have one exclusive mob,the Husk.Would more interesting adding a exclusive mob to taigas,savannas or even mushroom islands (i know that mobs dont spwan there btw).