Markdown files allow embedding images in it. However it requires the image to be hosted at some location and we can add the url of the image to embed it.
Example:

We can use services like imgur or other services to host the images and use the hosted URL.
What I'm going to show is just a quick and dirty alternative to the above mentioned image hosting services.
Once you have created a Gist, you can add comments to the Gist if required. We'll be using the features of this rich text editor of comment.
1) Pre-requisite : Create a gist with atleast one file.
2) Copy + Paste the image into the Comment field.
OR
Drag and drop the image into the Comment field.
The image will start uploading to Github servers.
3) Once the image is uploaded, the Url link to the hosted image is visible in comments field
___Copy and Use this link in the .markdown file___
````
4) Save the markdown file. And you'll see the image placed inline in the markdown file. Done!