Please, no enveloped postcards. I like the traveled look. Please, please, please do not write the Postcrossing ID on the bottom of the postcard when it is traveling to the US. The US Postal Service marks over IDs on the bottom making it difficult to register.
Though I do try to match postcard theme to profiles when I'm sending postcards, I'm not at all fussy about the type of mail I receive. Really. Below are just suggestions. Please do not go out of your way to find something special. All mail is special for me.
Postal theme of any sort are greatly appreciated. I also like mail featuring amusement/theme parks, fountain pens, beverages, food, pretty doors/windows, reading, and birdhouses/birdfeeders. Mailart is always fun. But, really, as I wrote in the second paragraph. whatever you send is special. You can even mail me a letter or a folded card instead of a postcard, if you wish. Really, I am not fussy at all. I just like to get mail.
I do NOT appreciate religious cards or religious quotes, including holiday cards. Save those cards for someone who will appreciate them. I do not consider postcards of churchs/cathedrals/mosques/temple or any other religious building a "religious" card. I think of them as architectural achievements.