Many have no doubt noticed the smileys are smaller that is only on the list to the right they are new for the shout box and have to be listed there, you can use them but there are many others you can use by either typing in the short cut if you know it or you can Click The "View more smilies" link (under the little smileys) there are currently three page of full sized ones to choose from.
A few Pics they help
And all the smiles: