Ah, it turns out that perhaps flushing the hard disk may be the better way. The script I mentionned wasn't really that at all unfortunately, it was simple a series of "Delete" commands in PostScript that were uploaded to the printer.
In order to use something like this, you would need to actually know, beforehand, what files you want to delete. For example, when uploading new photos, you keep a list on the side (in a database for example) where their time to live and size are kept. You would then build your PostScript deletion file through a query in that database.
The format for the deletion is this:
%!PS-Adobe-2.0
FILENAME deletefile\n
FILENAME2 deletefile\n
You then have to send this file to the printer, for example through an LPR Queue, in Passthrough mode (no document).
Please note: This information is provided as-is with no responsibility or warranty on our part. We cannot be held liable if deleting files on your printer causes the printer to stop functioning. We strongly advise contacting your printer manufacturer for further tips and perhaps alternate, safer, methods.