>>FIND
<a href="javascript: x()" onclick="DoPrompt('image');" title="{$lang.IMAGE_ALT}" alt="{$lang.IMAGE_ALT}"><img id="image" onmouseover="raiseButton(this.id);" onmouseout="normalButton(this.id);" onmousedown="lowerButton(this.id);" class="markup_panel_normal_button" src="{$config.BASE_URL}/images/{$style_array.markup_panel}/image.gif" /></a>
>>ADD BELOW
<a href="javascript: x()" onclick="DoPrompt('youtube');" title="Video" alt="Video"><img id="youtube" onmouseover="raiseButton(this.id);" onmouseout="normalButton(this.id);" onmousedown="lowerButton(this.id);" class="markup_panel_normal_button" src="{$config.BASE_URL}/images/{$style_array.markup_panel}/youtube.gif" /></a>