VSO REST API - IdentityImage only works with basic authentication?

Hi

I'm using the VSO REST API to get all members in a team, from there I'm getting the ImageUrl of the member. If I just bind an Image control to ImageUrl it's blank because VSO requires that I be signed in to get a profile picture... so I created a HttpClient and set my Authroization to OAuth and gave it my access token. This just returns a 403 :  Forbidden response... But if I use basic authentication, then everything works fine?

Is basic authentication the only method to get profile images from VSO via the REST API?

Thanks in advanced