I'm 39 years old and I live outside of Washington DC with my husband and two small children (ages 3 and 5). I started collecting vintage postcards many years ago and have over a thousand. I have been selling off some of that collection, plus vintage stamps from around the world at my shop on Etsy, http://www.etsy.com/shop/agnesofbohemia.
I love vintage postcards, but it definitely doesn't have to be. I also love any cards that are weird or creepy or scary or of classic actors and actresses from your country, and anything history related. I also like postcards of mythical figures from your country. Some other cards I also like are cards of prisons, any thing crime related, mental institutions and also cards related to local fashion.
I love learning about the history of the place I am receiving the card from.
In the end, I love all cards!