HTML Canvas: drawImage with 2×2 tile on an isometric map

Hi I am trying to draw images on an isometric map within HTML canvas element.

I can do that without problems using one tile to render an image on the isometric map.
However, I would also like to draw images which use 2×2 tiles (so twice bigger than the normal ones described above) like this.
(1×1 presents one image on one tile while 2×2 indicates rendering one image on 2×2(4) tiles. Although the image looks fine, but it just renders 4 images on 4 tiles [= one image on one tile])
enter image description here

I found the same question here, but it doesn’t really solve the problem.
I also tried just make the image size bigger but it didn’t work properly.

Could anyone please help me to achieve rendering an image on 2×2 tile on the isometric map?

You can see the code here on sandbox

And entire code is here on GitHub