as you can't read out a folder with flash only, this will be a problem. on the other hand, i don't understand, why you wanna make multiple instances of one mc with the same name.
A solution could be:
- saving alle thumbnail file names in an xml file, perhaps also
with the full image file name
writing a function, which dynamically creates empty movieClips and loads the thumbnails into it and arranges the thumbnails in the way you want it.
- writing a onRelease function, which perhaps also creates an empty MovieClip for the full image and loads the approprate image into that MC an positions it. I wouldn't load the full image into the same MC like the thumbnail, because that would make a jump back to the thumbnail more difficult.
- assigning this function to the created thumbnail MCs
Otherwise you would have to use server-side scripts, wich read out a folder an give back the file names.
hope, that helps for a start.