When you go to Blocks - Add new - Text block you will see a tinymce editor. When you insert an image you'll see the Integrated custom plugin for inserting images. This dialog only support the contentType "image" instead of all content types that are based on the Integrated\Bundle\ContentBundle\Document\Content\Image class.
When multiple image content types have been found the Add new button should be a drop down with a list of content types (http://getbootstrap.com/components/#btn-dropdowns). All image content types will be visible, also when the workflow-bundle has been loaded and you don't have access (as in issue INTEGRATED-654, this will be fixed later).
The content types also need to be added to the search filter.
Note: there is also a bug which makes the image invisible, but that will be fixed in another issue.