In fact, after a lot of thinking, me and my friend have come up with a lot of new options for trophies (maybe XenForo can introduce an easy way where we can create our own trophy criteria?).
1. Award trophy for number of threads created.
2. Award trophy for number of likes received on first posts (threads).
3. Award trophy for number of replies received in a topic created by user.
4. Award trophy for number of followers/following
The list could be endless, for us this is currently our list other boards may have bigger lists for creating trophies. It'd be amazing if XenForo had a easy method to create trophies based on custom criteria.