Instead of magnetic paper and adding magnets, just print on regular paper and then laminate (if you want it stiffer). Then use magnetic tape and put a 1" piece on each corner. It worked great for us and was so much less expensive than magnetic paper.
Another suggestion: buy the magnetic photo sleeves (they come in all sizes up to 8 x 10) and print your images on photo paper. Then you can switch the images around in the sleeves as you mood, or the theme of the day, dictates! This way you can print all of you fab ideas and get to use them without runnig out of door space!
And put your door # on the front of the magnet; that will make it less likely to be stolen. No one will be able to display it on another door without it being obvious!