Very impressive work dude!
Vitaly Okulov has shared a great video on speed level design Unity. The artist took his own package of assets to build an atmospheric fantasy village.
No advice on composition, but it is still a nice example of how you can assemble scenes. As you can see, the artist used a special designed tool for easier objects placement.
Did you like the village? You can build your own one with the help of package from Vitaly and his wife. A brilliant set of stylized PBR models, materials and particles in a cute fairytale style is waiting for you. The pack includes modular terrain and over 100 objects for populating the world. All models are optimized and mobile-friendly. What is more, you’ll get an Object Placement Tool — the tool demonstrated in the video.
You can also check out a free PC-demo.