A future version of the client will support the <viewFormat> tag for both <Icon> and <Url>. <viewFormat> is a string which may contain any of the following:

[bboxNorth] [bboxSouth] [bboxEast] [bboxWest]
[lookatLon] [lookatLat] [lookatRange] [lookatTilt] [lookatHeading]

The client will replace each "variable' with the proper value and send the final string in the url, e.g.,

<viewFormat>BBOX=[bboxWest],[bboxSouth],[bboxEast],[bboxNorth]</viewFormat>

is the default value and is the WMS specification.

<viewFormat>LOOKAT=[lookatLon],[lookatLat],[lookatRange],[lookatTilt],[lookatHeading]</viewFormat>

will return the camera parameters.

Note that <viewFormat> allows you to specify any combination of built-in variables and your own text.

If you have any issues with this, speak up soon.