If you are able to write a script that puts files in a certain folder then it is not much harder to actually have those files tagged - and as Colin mentioned I think someone has already done this.
If not, take a look at the flickr.pl script. It basically tags files through a messagesend command. Any script could do the same.
Yes, I know. I already played with the flickr.pl and the MessageSend. But again... the feature request is for a simple check box with a folder location so that the flickr scripts will tag photos in that location. I can script out quite a bit, but that doesn't help other people does it? I am suggesting this so that the app is friendly to the moms and pops. If LinuxMCE is going to appeal to the masses, simple things like this will make the product that much better. Just a suggestion, not a big deal really.
Anyway, colinjones already kindly answered my question. And it is good news.