Thanks but it wasn't what i wanted to do .
I fixed the problem (it was lower in the CSS, the .ossn-chat-windows-long .friends-list-item .name class ).
Thanks to have took on your time to try to help me

I see. I thought you were talking about the Chat Window where users type in their messages.

On the the friends list on the right and enlarge the icons, try this:

.ossn-chat-windows-long { width:125px; }
.ossn-chat-windows-long .friends-list-item .friends-item-inner { 100px; }
.ossn-chat-windows-long .friends-list-item .friends-item-inner .icon {
     height: 100px;
     width: 100px;
}
.ossn-chat-windows-long .friends-list-item img{
    width: 100%;
    height: auto;
    border-radius: 100%;
}

Sorry i finished to find the block to modify but i still have the problem of the pseudo on the picture ...

Thanks a lot Rally Homelancer. I tried your component with your script but nothing changed . I guess i was wrong in my request.
I would like to enlarge the bar on the right where all friends are listed. For now the pseudo of the member begin on the pic beside the pseudo.

You can change it from the CSS of Chat component at OssnChat/plugins/default/css/Ossnchat.php or you can install Homelancer Custom CSS/JS and add these lines to the custom Non-Admin CSS/JS:

.ossn-chat-base .ossn-chat-bar {width:255px}
.ossn-chat-base .ossn-chat-bar .friends-list,
.ossn-chat-base .ossn-chat-bar .friends-list .data{ width:250px;}
.friend-tab-item .data .message-sender .text .inner,
.friend-tab-item .data .message-reciever .text .inner{max-width:200px;}

you can also use the classes above to search them at the CSS file at OssnChat.php