Gas 13 is putting on a pixel art collaboration called PixelStamps.  Basically, you make an 80x96 or 160x96 stamp, read the submission rules and send it to Gas 13.

Pixel Art Rules...

- current theme of collection is "characters",
- all stamps have to be pixelated,
- a fully pixelated or framed stamp; it is up to you,
- no animations,
- *.gif or *.png (8 bit),
- please add your country name to your stamp (could be written in your native language);
- remember, don’t add your stamp price,
- multiple submissions are allowed.