If Maslow were still around, I think he would have a separate hierarchy of needs for Christmas cards, and I believe it would go as follows:
First, there is the basic essential human need for a Christmas card. This is the basest of all cards, consisting of the pre-printed greeting and a signed name. Not ideal, but still better than bills and craft store coupons.
Next we have the card with the letter but no pictures. While not including a picture is disappointing, points are gained if the letter is funny. Points are lost if you talk too much about your 3-year-old speaking multiple foreign languages or mastering long division, but are regained if you share a story about them saying/doing something embarrassing in public. Any points gained by including a letter are immediately revoked if you write more than 2 pages. And really, if you write that much it had better be good.
Level 3 involves a card, and a letter, AND a picture. You are approaching perfection in the Christmas card world, but lose credibility if the picture is only of your kids. I don't care how cute you think they are, they're usually not all that. But major points for including all three card elements. However, when pictures and letter are included, actual card loses some significance and may not be necessary. Again, any points lost can be regained if you bring the funny.
Finally, self-actualization on the Christmas card pyramid. This is achieved with or without a card, but most definitely includes a letter of some sort which must consist of at least one self-deprecating reference and zero mention of your pets. Critical at this level is the photo that includes a picture of everyone in the family regardless of weight gain or hair loss. Now if you'll excuse me, I need to solicit a Photoshop tutorial on "How to shave off 30 pounds from your Christmas card photo."