If someone is looking for a solution to this, the trick I found.
so basically the solution is to pass the image url to the sent url field and not pass the parameter of the sent url image.
so instead:
{ "comment": "Check out developer.linkedin.com!", "content": { "title": "LinkedIn Developers Resources", "description": "Leverage LinkedIn APIs to maximize engagement", "submitted-url": "https://developer.linkedin.com", "submitted-image-url": "https://example.com/logo.png" }, "visibility": { "code": "anyone" } }
which will give: 
you pass the following:
{ "comment": "Check out developer.linkedin.com!", "content": { "title": "LinkedIn Developers Resources", "submitted-url": "https://www.example.com/someimage.jpg" }, "visibility": { "code": "anyone" } }
which will give the following:

Please note that I do not pass the sent-image-url and description in json. The description does not appear in the message, so it makes no sense to transmit anything in this field.
j4rey89
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