We automatically select event icons depending on the terms in the event title. To trigger a particular icon, try including the keywords in the title.
For example, if you want the Coffee icon, try using a title such as "Coffee with Joe". Alternatively, try following a format such as "Catchup with Chris [Skype]" or "Going to NYC! [Bus]".
Here's a list common icons that we support. Be sure to try out variations of the terms as well as terms in other languages.