Best approach would be a layout override for the module or a custom layout for it. There you'd add the onlinestatus field output however you'd like. The quickest is probably to just use the "User-text" parameter within the module with something like the below.
Code:
<div class="cb_template">
<div class="cbOnlineUserContainer">
[cb:userfield field="avatar" reason="list" /]
<div class="cbOnlineUserStatus">[cb:userfield field="onlinestatus" reason="list" /]</div>
</div>
</div>
You'll need some custom CSS for re positioning the online status wherever you may want it. The below CSS should give what you're wanting.
Code:
.cbOnlineUserContainer {
position: relative;
}
.cbOnlineUserStatus {
position: absolute;
left: 0;
bottom: 0;
font: 0/0 a;
}
.cbOnlineUserStatus .fa {
font: initial;
}
The module has no functionality for outputting custom css so you'll likely need to add it to your Joomla template or try using CBs built in CSS override feature below.
www.joomlapolis.com/blog/kyle/18711-template-css-overrides-made-easy