His commissioned works were mainly history paintings that included religious and mythological subjects as well as hunting scenes. He painted portraits, mainly of friends, and self-portraits, and later in life he painted several landscapes. Rubens designed tapestries and prints as well as his own house. He also supervised the short-lived decorations of the Austrian Cardinal-Infante Ferdinand's royal entry into Antwerp in 1635, and he wrote a book of illustrations of the palaces in Genoa, published in 1622 as Palazzi di Genova. The book helped spread the Genoese palace style throughout northern Europe. Rubens was an avid art collector and owned one of the largest collections of art and books in Antwerp. He was also an art dealer and is known to have sold a significant number of works of art to George Villiers, 1st Duke of Buckingham. He was one of the last great artists to consistently use wooden panels as a support medium, even for very large works, but he also used canvases, especially when works had to be shipped long distances. For altarpieces, he sometimes painted on slate to reduce reflection problems.