how can you refer to an image on another machine?

My webserver (a Siteplayer) is sitting behind my Linksys router, with a port
forwarded to it on the router. The problem is this: how can I have the HTML
code in a siteplayer page, webcam.html, reference an image file video.jpg
which is located on another machine on my home network? ie, HTML code on the
siteplayer page webcam.html:

<img src="//Constor2/shared/video.jpg">
or
<img src="//192.168.1.100/shared/video.jpg">


will both display video.jpg fine as long as webcam.html is called from a
machine inside the router on the home net. But if I try to get to that same
Siteplayer page webcam.html from outside the router with a port forward,
like http://24.56.78.922:2222/webcam.html, the page comes up but there's no
image, just the box with the red x. How can I make the image display from
outside the router?

Is this impossible, or is there a clever way to code it so it'll see the
file on the other home-net machine? perhaps OBJECT embedding? Any advice
most appreciated!!

Thanx DB