First, as long as it’s for your own personal use, you can also just print out postcards that you find online from all over the world. If you really want them to be as thick as postcards, you could print them on photo or brochure paper (to get the best color), then glue them onto cardstock and trim to postcard size.

I’ll do a Google "Image Search" for you to see what I can turn up. Actually, it would probably be better to do an image search for a particular state or country… Here are some examples:
http://images.google.com/images?sourceid=navclient&ie=UTF-8&rlz=1T5GGLL_en___US278&q=India+postcard
http://images.google.com/images?sourceid=navclient&ie=UTF-8&rlz=1T5GGLL_en___US278&q=postcard+Montana

By the way, here a link to the page at Google which is for their "Image Search" so you can ask for any other state or country, etc., you want:
http://images.google.com

If you don’t know how to "grab" photos from the internet, then print them out or save to print out later, basically just right-click your mouse on almost any image you see online, then select either Copy or Save.
If you copy it, you can "paste" it into photoediting software or even into Word, then print it out.
If you save it in your computer system, you can keep it and print it out any time you want.
(You’d have to consult your own software for how to change the size of the image, etc, before printing.)

HOWEVER, it also looks like there may be individuals and maybe even groups that like to exchange postcards for their collections too, like this one:
http://gemsworldpostcards.blogspot.com/2007/12/first-postcard-from-velu.html
You could ask that person how to get more postcards too, or you could look for more people who do that (check out these good links):
http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T5GGLL_en___US278&q=collect+postcards

HTH,

Diane B.