Most email wallpaper strikes me the same as handprinted business cards or "business" email addresses that end in @aol.com or @yahoo.com. In other words, the sender seems somewhat unsophisticated. I don't hate it, but it doesn't foster great confidence in the sender.

Typical e-cards do seem too easy, and they can't stand on my bookshelf or hang on a bulletin board. That doesn't mean e-offerings can't have a personal touch, though: A holiday computer wallpaper or smartphone app shows that the sender put some effort into the greeting. Make it downloadable with a link, not an email attachment, and your consideration shows even more. I'm 55, by the way.

Great points, well adapted to writing. I would only note that sometimes with point two the very opposite is true. That is to say, when a writing task seems too big to tackle, whittling away at the easy parts for awhile can make it seem less daunting and build some momentum to get over the hump.