I got the problem solved. It was not related to the theme.
My .htaccess contained a rule for hotlink protection:
<IfModule mod_rewrite.c>
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{REQUEST_FILENAME} -f
RewriteCond %{REQUEST_FILENAME} \.(gif|jpe?g?|png)$ [NC]
RewriteCond %{HTTP_REFERER} !^https?://([^.]+\.)?domain\. [NC]
RewriteRule \.(gif|jpe?g?|png)$ - [F,NC,L]
</ifModule>
As I removed the rule Edge started displaying images in the hero again.