In Windows Live Messenger, you can use Emoticons express your moods. Windows Live Messenger includes a gallery of emoticons that you can use; but should you wish, you can also create your own emoticons.
To create emoticons natively using the in-built Windows Live Messenger feature, please visit this TWCF thread.
To make emoticons for Messenger directly online by a few simple steps, visit FGTMakers. Select the text, animation, background, and do much more at this website.
To browse all your Windows Live Messenger custom emoticons, and save them to your hard disk for backup or any other purpose, try MSNEmoticonsToGif from CodeProject.
EmoticonMadeEasy is a program that allows you to backup your Windows Live Messenger icons, import/export emoticons, import Yahoo Smileys, import images or icons from local machine and convert them into WLMessenger emoticons, and share your emoticons between computers or accounts, or share with your friends.
While I have not tried these freeware apps, they are reported to work on all Windows and the latest version of WLM too! If you know of any more such or if you have any feedback on these, please do share in the comments section.