I click my name and there's a head-shaped icon with numbers on my profile.

Although it might not look like the player's head, it is a number of head trophies (commonly referred to merely as heads by the playerbase). These are gained or lost from fighting - most commonly, one would gain heads by attacking and defeating a player with some of these heads, and lose them by defending against and losing to another player.

It is also possible to gain them from bounties, and rarely, other activities.

In the past, contests were run where players would attempt to collect these and hold them in specific locations. While such contests have not occurred for some years, their functionality remains, and some players still choose to collect heads for fun, or for other purposes, which are left to the player to discover.