1) I've read you can create a HttpModule(HttpHandler?) that will stream  an image  as you wish. But then your going way beyond just one control. And that's not design  time.

2) There's a "Image to HTML" sample on:

www.gotdotnet.com/.../keywordsrch.aspx%20Server%20Control

It's as slow as Forrest Gump on a bad day, but might give you what you want in the designer.

3) Overall.....I recommend saving the image to a file and setting the URL.

4) "If you don't want to let on then please  can someone just tell me if it can be done and I'll (eventually) figure  it myself."

That line strikes a chord. Seems to me that MS and all the "insiders" are hording information on NET. Trying to find  anything beyond the basics is next to impossible unless you can afford an MSDN subscription or the 50 bucks each for a series of 500+ books written by current/former MS employees or MVPs. And even then, the info is skimpy. I'm troubled that I can honestly say-- I've learned more with a de-compiler I downloaded, than anything else.