I don't have my files here to check, but it should be relatively simple - one could either invest a bit of time to check private forum access and write the code to show the image (which might slow down a busy site), or for no slow-down a little less time could be invested to use one of the provided extra profile fields to fill-in during the time used to give the same person access to the private forum, then all the template editing needed would be just a call to the profile field.
If no-one else gets it I should be able to sometime this weekend, right after a few other things promised
