One really cool thing we did here recently at ESL Partyland was get ourselves some custom t-shirts for everyone in the office. And we got thinking about how cool it would be if everyone could have their own t-shirts, custom-made just for them.
If you are learning English you could put a message on your t-shirt with something like "ESL Student", "Practice English with Me", or "I Love English" (with a heart).
If you are a teacher maybe you could get a bunch of T-shirts with English puzzles on them and wear a new t-shirt to class everyday. That would be a great little game for students and something that would really leave an impression.
And, if you work for a larger ESL company, why not get a bunch of custom t-shirts with your logo and give them out to your students. That's a great way to do some marketing.