Do you have it on a Photobucket or Flickr account of some sort? You could do that and embed an image with the tags.
Under "Attach Files", click the "Manage Attachments" button. You should see the Manage Attachments box pop up. If it doesn't, temporarily turn off your browser's pop up blocker.
From there, you will see five blocks of files you can upload. If you have the flat on the computer, you click on one of the five "Browse..." buttons, particulary the first one you choose to upload. Find where your flat is stored and click "Upload". That attachment will be posted below your post for the rendering gurus to access quickly and upload to their 3dsMax scenes.
Remember that the mask layer is OFF, not deleted. Hopefully that made sense. Try that and see what comes up.
SRD actually has an image hosting service built in, just click on the image hosting tab in the blue bar, upload your image, and then copy and paste the link that starts with