Calendar = 1-31 images for 1-31 days of the month.. and only updates once a day
Weather = -XX to +XXX images for all of the different temps.. plus it would need to update itself at a given interval, which uses data and battery life, and people would complain, and then they would have to code in a turn off auto update feature, and then people would want more than one temperature showing, so they'd have to find a way to show two temperatures. Then people wouldn't know what temp it was showing, so it would need to say the location name.
..... can o worms that there feature is! Though it would be nice.