Possibly, if you were not born in July, you have never noticed this phenomenon. But calendar-makers quite typically save all their worst photos or illustrations for that month. Perhaps they think everyone will be on vacation, will not give their wall-calendars so much as a glance, and will therefore not even notice their laziness.
But I notice. Am I the only person who opens a calendar directly to her birth-month page to see what is represented there? Quite often I am tempted to make my calendar-purchase decisions based on the picture staring at me out of July. Often, but not always. If it were always, I would never buy any calendars at all, because July calendar art is usually ugly, or boring, or tritely patriotic, or a bad guy. This year I bought a Beatrix Potter calendar on sale in mid-January, partly because it was on-sale in mid-January, and partly because even though the character respresented on the July page is a fox (one of the bad guys, though I do not recall from which story), it's an engaging illustration. Sometimes you have to settle.
Roommate-Rachel, however, has saved the day. (Or the month.) She has a Lord of the Rings character-portrait calendar on which we write our weekly work-schedules, hanging in the kitchen. Staring mysteriously out at us from behind her glistening white hood is Galadriel in all her elvish glory. I have always like Galadriel. I've pretty much always liked elves, too. I fully endorse this calendar.