That's really neat idea. It could be any shape or color, but used consistently in every piece.
His hearts were always one of the repeated colors he used in the lamps and let me tell ya, you had to hunt for it, which is good, that way it is not a in your face kind of thing.
Years back when I did ceramics it was always a hot topic, whether or not you should sign your pieces. When I was painting and doing charcoal, the rule was, it wasn't finished till you signed it.
But for some reason in the ceramic world, back then, many found it offensive to have the artists name and or logo on the piece. Go figure.
If my piece was a one of a kind or part of a limited series, I always signed it, but not in mass production of items. The signature would be on the bottom of the piece out of sight of the art work.