Have had no problems in my own game doing this with the Last Name Copier:
http://www.modthesims.info/download.php?t=289073Off the top of the head, don't recall if it will automatically work with infants without making them selectable first (which can be dangerous for the game) -- but regardless, will work for any Sim from toddlers on up.
Should be compatible with AL, which somewhat altered the naming internal bits of the game (the post linked above is mute on that), but no guarantees on that.
Should the painting object itself not fit in with your decor, just delete it after making the name change (the new name will still continue to be in effect).