Is putting furniture on your wedding registry practical or tacky? That depends on your guest list. If you know your friends and family have the means and the money to buy you expensive furniture, and you genuinely need it, then go right ahead. But since most stores offer a discount on any unpurchased items from the registry, many couples register for furniture solely to receive that discount.
The problem is your guests don't know that. And if you have a large number of expensive furniture items on your registry, some guests may feel obligated to spend more money than they'd really intended to spend.
If you're really desperate for cash to spend on furniture, you might consider adding some store gift cards to your registry, instead. If you're uncomfortable with that, simply let your family or wedding party know that you would prefer gift cards, and they will spread the word to your guests.