Custom (image) Content Provider - image doesn't render in edit mode

Hello,

I'm in the middle of implementing a custom content provider to server images from an external dam system.

I've got almost everything running, except, I have no images in on page edit mode.

My content provider returns a custom IContent type that inhertits from ImageData, this to blend in as best as possible in epi.
Behind it I have a custom blobprovider to stream images from the dam.

Thumbnails in the shell works, as well as the rendering on the public site. But I don't see any images in edit mode.
And I think the problems lies how epi generates it url's.

If I use an image from de default media library, the url to an image in edit mode is the following:
http://localhost:1812/EPiServer/CMS/Content/globalassets/en/demo/cotton/farm2.jpg,,14?epieditmode=False

But when I use an image from my provider, it's like this:
http://localhost:1812/EPiServer/CMS/Content/en/dam/9FCBB804-89E5-4443-8D969A9265D74B3B-home-banner.jpg,,1__bynder?epieditmode=True

If I open this url, it triggers 2 requests:

1. http://localhost:1812/EPiServer/CMS/Content/en/dam/9FCBB804-89E5-4443-8D969A9265D74B3B-home-banner.jpg,,1__bynder?epieditmode=True
   Content-Type:text/html; charset=utf-8
2. http://localhost:1812/EPiServer/CMS/Content/en/dam/9FCBB804-89E5-4443-8D969A9265D74B3B-home-banner.jpg,,1__bynder?epieditmode=False
   Content-Type:image/jpeg

When I use the edit action menu in the assets pane, it immediately renders the following (correct?) url:
http://localhost:1812/EPiServer/CMS/Content/en/dam/9FCBB804-89E5-4443-8D969A9265D74B3B-home-banner.jpg,,1__bynder?epieditmode=False
Content-Type:image/jpeg

Does anybody already encountered this? Any idea how to resolve this?

Many thanks,

bob