i'm looking for a mod (pic inside)

[Darat]

You could perhaps do it by altering the CSS style, for example putting this in the "Additional CSS" section of your style would put the username in a block - just alter the colours to suit:

.bigusername {
display:block;
background:#ff6699;
border: 1px solid #ff3333;
font-size: 14pt;
text-align: center;
text-color: #ff3333;
}