The #1 thing that is top on the list for a housewarming gift is a bottle of wine.
Wine makes a great housewarming gift.
Other good housewarming gifts are flowers, gift baskets, coffee and tea baskets, nice paintings and other wall hangings, and even bread and salt.
Bread and salt was a Traditional housewarming gift and still is in Israel as a nice way to welcome someone to their new home.
Pineapples also make a great housewarming gift and symbol of warmth and hospitality.