In many games there are rewards such as gold coins, points, etc. When these rewards can be used to purchase in-game items, it motivates the player to keep playing.

Let's say we have an online game, poker, Yatzy etc. What type of reward would keep the players playing if there are few in-game items available to buy, or none at all?

What I am looking for is a reward system that entices the players to play more in a game environment where there isn't that much to purchase. For example, there isn't much to buy in a poker or Yatzy game with the gold you win.

I guess having some titles that are added to the userid is one way, or maybe purchasing a logo for the id... A leaderboard is another.

Any thoughts on this?