The presentation can be on anything and the more creative the better. Here is the official website with more info: http://www.pechakucha.org/faq

If you’re interested and want to present on a topic, sign up here:
https://docs.google.com/spreadsheets/d/1hQzar_a4jI6zq8ucPLCU9vpjCT0J2c5Is0ijee3jf0k/edit?usp=sharing