Entity with image field: image is not rendered properly

I have an entity type set up with an image field with multiple values. When I check the entity's page provided by ECK, the image does not appear as it 404s out. It seems the image tag is pointing to the root of the Drupal site instead of a picture. The same happens when the entity is used in a node with EntityReference and trying to display it with the Rendered entity option, Full display mode (which earlier has been configured to display to image with an image style).

When the same entity is display with Views, it's showing the images properly.