There is an event being hosted in Los Angeles for artists. All you need to do is have a Twitter account, follow the official profile of the exhibition, email to register and then create a postcard sized piece of art and send it in. (So, don't worry if you live in the UK, China or anywhere else!)
The cards will be displayed in their exhibition and must be 100% handmade. (No printing of digital work.)
If you are interested, go ahead and read about it a little more here: