You’re welcome to use “iNaturalist Ambassador” on your shirts. For Ambassadors, we ask that you don’t represent yourself as iNaturalist staff, if anyone asks. You can also use the logo & wordmark (downloadable on the Press page) as long as you use them as-is with no alterations.
Thanks for being an ambassador and holding events! Also feel free to email ambassadors[at]inaturalist.org if you have other ambassador-related questions that you need staff to answer.