For example, I have a.jpg
on the google drive.
-
Right click the image and click
Share...
-
Click
Advanced
and change theWho can access
option toPublic on the web - Anyone on the Internet
- Copy the
link to share
and you will have something like
https://drive.google.com/file/d/<FILE_ID>/view?usp=sharing
- Copy the <FILE_ID> to make a link like this:
https://drive.google.com/uc?export=view&id=<FILE_ID>
- Insert image in Markdown as ususal using the link from step 4.
For example:

Example: I have this octocat image in google, and its file id is 1913oZeBZPBNiUuk8gu3ZSbLBA2l_VQtG
. You can try 
in your markdown file or even in this answer.
Hope this helps.