Форумы / Cotonti / Support / group icon on avatar

Hello everyone.Could someone help me on this:

In forum and in comments i want to put the group icon directly on the avatar(like a watermark or something.In comments the avatar's tag is

{COMMENTS_ROW_AVATAR}

.
I understand that it need's to be written something like this:

<div style="background: url(' {COMMENTS_ROW_AVATAR} ');" width=100% height=100%><img src="{Com_row_groupico}"></div>

but dont understand to the end how it really should be...