Interesting that American Greetings now offers a few ecards just for National Library Week and reading in general. I set up something like this several years ago for my member libraries, although only one of them actually used it (and has since discontinued using it). You can still play with the demo, which used the Library Media & PR Read graphics. I used to change the postcards seasonally, which was kind of fun.

I still think this would be a great project for ALA to do on a national level.