I have never really found myself needing more smileys than the ones provided by RIM but others are fans of the many smileys available in third party apps. S4BB decided to offer a free app called Easy Smiley Pack for BBM which gives you access to loads of smileys from a simple BBM menu option. The app works well but has one major issue since it does not show you a preview of the icon (only a text description) before you insert it. Still it is free so you cannot really complain.
You can pick up the free Easy Smiley Pack for BBM in App World