It seems unlikely they'd make 1 item from the set available in-game and nothing else, so it might well be that like Imperial motifs they're just rarer than the other styles.
I've just found a guild trader with 'Imperial Lightpost, Pair' for sale.
I've just found a guild trader with 'Imperial Lightpost, Pair' for sale.
I saw one of these listings too, and contacted the seller. He said it came with his house when he bought it, and he didn't know how to get any more. All houses seem to have a few decorations in them, and I believe they're tradeable if you buy the house with gold (rather than crowns).