Yes there is actually.
You need to get the sources of the firmware and recompile them yourself after editing the webpages.
you probably noticed the folder "/www" on your router.
that folder contains all the webpages and images.
With some quick editing you can change colours, text etc.
but you cannot save them in "/www" since the directory is not writable, therefor you need to recompile the firmware with the modified pages;)
Example code:
<html>
<head>
<title>ASUS WL500W Web Manager</title>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<meta http-equiv="Content-Type" content="text/html">
<meta http-equiv="Pragma" content="no-cache">
<link rel="stylesheet" type="text/css" href="style.css" media="screen"></link>
<script language="javascript">
function redirect() {
setTimeout("redirect1()", 25000)
}
function redirect1() {
top.location="index.asp"
}
</script>
</head>
<body bgcolor="#FFFFFF" onLoad="redirect()">
<span class="wounderline"></span>
<table width="666" border="0" cellpadding="2" cellspacing="0" vspace="30" height="1">
<tr bgcolor="#CCCCCC">
<td width="666" height="125">
<table width="660" height="125" cellpadding="2" cellspacing="0" border="0">
<tbody>
<tr>
<td bgcolor="#FF0000" height="50" width="652"><b><font size="5" face="Arial" color="#FFFFFF">System Restarting!</font></b></td>
</tr>
<tr>
<td width="652" height="25" bgcolor="#FFFFFF" colspan="2">System is restarting! Please wait until home page of WL500W setting is shown up again.</td>
</tr>
<tr>
<td width="652" height="25" bgcolor="#FFFFFF" colspan="2"></td>
</tr>
<tr>
<td width="652" height="25" bgcolor="#FFFFFF" colspan="2"><font face="Arial">
<font color="#FF0000"><b>Note: It takes about 20 seconds.</b></font></font></td>
</tr>
</tbody>
</table>
</td>
</tr>
</table>
</body>
</html>