When you click the smiley face in your chat window, MSN Messenger shows you 60 basic MSN emoticons but do you really need to have quick access to :) and ;) to name just two, the ones you've known for ages? No! You want to quick-click your custom emoticons, because they are the ones with codes that you have a hard time remembering. But Microsoft has decided only to show your first 10 custom emoticons in the reference list.

If you have added 10 emoticons or less, that will do for you.
If you have added just a little over 10, you could click My Custom Emoticons and reorder the list a bit, moving your most commonly used ones upwards.
If you have added LOADS, then you got a problem that can't be solved without the use of an addon. We will have to call in the help of Messenger Plus!
Notice that after you installed Messenger Plus!, whenever you type the ( character in the text field of your chat window, another quick emoticon reference box will appear. And this is one you can entirely customize to your preferences.

This shortcut list will automatically show your Custom Emoticons (spread onto different pages if there's a lot of them). So hold ( and select any emoticon to insert it into your conversation. Clicking "Customize..." in the Quick Icons window allows you to edit the list and create a list of your personal favorites (you can leave out the standard MSN emoticons). Another great option is that you can glue a couple of codes together and create one-click emoticon series. Aahh.. how nice to have all your favorite emoticons right there when you need 'em!