=IF(YesNoColumnName=TRUE;"<img src='http://SharePointUrl/_layouts/images/cbChecked_locked.GIF' border='0'/>";"<img src='http://SharePointUrl/_layouts/images/cbUnChecked.GIF' border='0'/>")

=IF(YesNoColumnName=TRUE,"This is the text when the column is Yes","This is the text when the column is No")

=IF(YesNoColumnName=TRUE
    ,
    "<img src='http://SharePointUrl/_layouts/images/cbChecked_locked.GIF' border='0'/>"
    ,
    "<img src='http://SharePointUrl/_layouts/images/cbUnChecked.GIF' border='0'/>"
   )

="<img src='/_layouts/images/cb"
 & IF(YesNoColumnName,"Checked_locked","UnChecked")
 & ".GIF'/>"

="<img src=/_layouts/images/cb"
 & IF(YesNoColumnName,"Checked_locked","UnChecked")
 & ".GIF>"

="<img src=/_layouts/images/cb"
 & IF(YesNoColumnName,"","un")
 & "checked.gif>"

="<div style='font-size:25px;margin-top:-10px;color:darkgrey;'>"
&"&#974"
& 4 + YesNoColumnName
&";</div>"