in html mode, copy and paste this code
at the top of the page :

<table align="center" bgcolor="#......" border="0" bordercolor="#......" width="80%">
<tbody><tr>
<td>

fill up the page, and put this code at the bottom of the page :

</td>
</tr>
</tbody>
</table>

and press : Edit my profile

technical infos

bgcolor="#......"
(it's the background color replace ...... with the color code in html - ex. for white it's FFFFFF, orange is ff9900)

border="0"
(if you don't want a border around the table, otherwise put "1" for a thin border... "2" for a thicker border)

bordercolor="#......"
(if you chose to have a border, it's the border color.... replace ...... by color code in html)

width="80%"
(it's the width of the background in % - to have it at its maximum put "100%"

in html mode, copy and paste this code
at the top of the page :

<TABLE bordercolor=#...... cellspacing=5 cellpadding=10 background=http://background_picture_address border=2>
<TBODY>
<TR>
<TD align=middle>


fill up the page, and put this code at the bottom of the page :

</TD></TR></TBODY></TABLE>

technical infos

bordercolor=#......
(if you chose to have a border, it's the border color.... replace ...... by color code in html)

cellspacing=5
(border width = 5)

cellpadding=10
(margin around what's in the table towards the border)

background=background_picture_address
(choose a picture and host it at http://imageshack.us to have an address for this picture - ex : http://img307.imageshack.us/img307/6351/1769370dx8.jpg)
border=2
(thickness of the border around the table)