Heat the oven to 400 degrees. Arrange the oven racks in the center and upper third of the oven. Spray 2 large cookie sheets with cooking spray. Mix the sour cream, Parmesan cheese and artichoke hearts in a medium bowl. Remove the biscuits from the package and on work surface, press each into 5 1/2-inch round. Place the biscuits 2 inches apart on the cookie sheets. Press out again if the dough shrinks back. Top the biscuits evenly with 1 1/2 cups of the Italian cheese. Spread evenly with the sour cream mixture. Top with tomatoes, thyme, and remaining 1/2 cup of the shredded cheese. Bake for 10 to 13 minutes or until deep golden brown and the topping is bubbly, switching positions of cookie sheets half way through baking for more even browning.