i have try to make a plugin. It create an Imagetag. When you want, it can create a thumb and store it to the webserver (chmod 777). I custom it create a "selflink" to the original picture and open it when you select the picture. Jpge, png and gif should be possible.
You can downlod form: http://robbyber.xail.net/cms/index.php?page=Download
I hope it dosen't work only on my page

Bye RobbyBer