First, open the "widget_members_online" template and find the following code;
Replace with the following code;
Then find this code immediately below;
Replace with this;
That's it! 
It is my own arrangement, I hope it will benefit you
Kod:
<ul class="listInline listInline--comma">
Kod:
<ul class="listHeap">
Kod:
<li>
<xf:username user="$user" rich="true" class="{{ !$user.visible ? 'username--invisible' : '' }}" />
</li>
Kod:
<li><xf:avatar user="$user" size="xxs" img="true" /></li>