I am not sure they will render as images in the app but you can add smilies to your post using text and they will display for those viewing the full version of the site. As an example the standard smile can be added by using a : and ) together (like this)
You can see the replacement text here on the full smilie list :
http://www.keystonerv.org/forums/misc.php?do=getsmilies
Example: