Fruit is really one of the most traditional Chinese housewarming gifts. If you bring flowers, make sure they're not all white--white flowers are used at funerals a lot. Or food...most of the Chinese families I know like food. You could also bring wine if the family doesn't have an aversion to alcohol. Most Chinese families I know prefer to shop for their own home decorations so bringing paintings or wall hangings or even dishes is probably a bit weird. If you really are at a loss for what to bring, prepare two red envelopes with the same amount of money inside each of them. There is no definite amount of money you have to put in each but if I was preparing a housewarming gift and I knew the family fairly well I would put at least 50-100 HKD in each. This is "lucky money" and although it is primarily handed out during Chinese New Year, it is also presented at weddings, birthdays and other special events.