Hi there Henning,
I've discovered the issue. It is truncation settings located here:
EasyBlog>Settings>Layout>Truncation
The truncation settings plays a part in determination the amount of a post's information would appear on the frontpage (the EasyDiscuss page you set it to).
I've checked the settings and you set the images to appear on the frontpage.
One more thing, because you use different composers for different posts, the truncation settings must be set for both EasyBlog's composer and the other composers.
You can refer the screenshot as shown here
http://screencast.com/t/URwZQ60rpw5
I've set that any post created using EasyBlog composer to show 1 image. Not sure if that is to your liking, but you can change it on the setting there.
I hope this helps!