I've gotten some great results using the following when making blueprints. https://www.turbosquid.com/3d-model/free for something to import. Get the .obj file for your subject. Convert to Voxel http://drububu.com/miscellaneous/voxelizer/index.html?out=vox&res=512 Save as a .vox file after importing an .obj file. Use MagicaVoxel for making changes along with figuring out the layers for laying out your subject in Minecraft & planning color. https://ephtracy.github.io/ Keep in your thoughts the how far out someone can view when planning scenes. 64 blocks out seems to be the max which results in a 128x128 area for your floor-plan but a viewer can run about so that the whole thing can be viewable from farther away.
I tried reproducing the plans for a certain dinosaur sculpture I found out on SMP2. A t-rex skull found at the link below and converted to .obj https://sketchfab.com/models/9a4adcd0ad62492799e3651dafeca95d# The .obj to .vox Now, to create the same thing in minecraft, slices are taken, layer by layer, and reproduced in game though careful planning. The last example I saw used bone-blocks.