Here are a few more for your list if you don't mind me sharing
Eat Cake Graphics: 15% off your next order after having something published using their stamps
Stamp LaJolla: Will give you goodies if you have something published using their images
Stamp Camp: will give you credit for more stamps if you have something published using their images.
Just be sure that you let the companies know you had something in a magazine. Many of the manufacturers are so busy that they do not have time to read and browse thru all the magazines :O)