ASCII smilies cause problems for translators, because the system reports unbalanced parentheses. Instead, please us icons such as [[Image:face-smile.png]] . Keeping the size below 15px constrains it vertically so that the text line isn't distorted.
Additionally, UserBase is linked to InstantCommons where you can search for other smilies or other images. You do not need any special addressing - they act as though they are uploaded onto our server.