Hey OWM, take a look at the row of icons just above where you type in the comment box. At the right hand side, second from the end, there's an icon that's a hash mark (#) with 'wip' in yellow (it's quite small so maybe a little hard to make out the details).
If you press that button, you'll get this:
### Latest WIP ###
Add that text via the button, then insert your image. This makes sure our image scraper can find your latest map and include it in the challenge thumbnails gallery, which you
can see here. Voters use this gallery to check out all the entries when it's time to vote, so you want to make sure your map is there.
EDIT: I've added the tag to your first comment. Your image should show in the thumbnails gallery now.