An interesting filter. I'm not sure it necessarily recreates cracked paintings, but it does give an interesting mural effect. Could be a good and useful filter with some work.
I have some suggestions, thing which seemed like they'd improve the filter and make it more useful. Nothing hard or big, but I think they'd be great improvements.
One of the basics if you're going to make it for aging something would be an ability to fade the picture. While there is some possibility for this in the picture transparency, it's not quite what might be wanted.
The other thing that could be rather interesting if improved are the cracks. Some variation to them would be nice. Some small distortion. Paint tends to chip more than crack. Something which could improve the cracks a bit, would be to allow a bit of the under painting or however you call it to show through. A threshold with minimum (suggest radius .5) following it could be used as a screener to select only larger areas for this (More hardcore FF users might have better solution). Adjustability of the scale of the cracks would also be nice. (On a particular picture the cracks ended up looking huge in relation to the picture size).
I like the basic effect and general look, but it's not quite where I'd like to see it. I think with a couple changes, it'd look even better.