Hello!
I am a beginner in three.js and I find it very interesting.
I have been using Pixel 2 live wallpapers since few days and they are absolutely gorgeous but I like dark wallpapers more, specially of universe. So I was thinking it would be awesome if I can make a simple interacting app in three.js and port it as Live Wallpaper somehow.
Google didn’t help much. I hope someone can guide me on this 
As far as I know, an Android live wallpaper is just a video or an animated gif image, so yes, you can use anything that displays on your screen.
You’ll need to capture a video (you can record from the browser using something like Nimbus, Awesome Screenshot or others) and you can set the browser window to the same resolution as your phone using Window Resizer.
Try the technique with some of the examples first to get it working.