I have stored a Markdown file and an image file in a Git repo as follows:
readme.markdown
images/
image.png<
My images where in the .bin/img/
folder.
I had to use below format to get an image:

Mind the <>

without the ./
works for me: https://gitlab.com/cirosantilli/test/blob/bffbcc928282ede14dcb42768f10a7ef21a665f1/markdown.md#image
I have opened a request for this to be allowed at: http://feedback.gitlab.com/forums/176466-general/suggestions/6746307-support-markdown-image-path-in-current-directory-s , but it entered into Internet void when GitLab dumped UserVoice.
In GitLab Markdown, you could add images to Markdown file in two different ways.
Inline-style :

Reference-style :
![alt text1][logo]
[logo]: img/markdown_logo.png "Title Text"
You could use any of the above method. In your case removing the ./
will be the solution.

For more on GitLab Markdown .
I had the same problem with my Logo inside of a readme.md in my Extension and with Gitlab (running on a Ubuntu-Server).
Ubuntu Version: 16.04.2 LTS
Gitlab Version: 10.3.4 56dc722
You can also use a snippet for image-usage in your readme.md by simply following these steps:
If you get the following error you forgot point 5:
The form contains the following error:
Content can't be blank
Now, if you edit the snippet again, you can copy the Image-Code looks like this:

to your readme.md file.
If you like to use a link also, it has to look like that:
[](https://your-destination.com)
Hope it helps other ppls