Is there a way of editing the icons on the desktop? If so is there any documentation for this ? is it at all posible?

Sorry, there is no possible way to edit the desktop icons in any sony ericsson theme, the desktop icons are in the firmware (well i don't think, i know you defenatly can't with the K700 and the T610),

Icons and more in themes? Do you mean the icons and it's effects in themes or the default desktop icons of the phone?

desktop phone icons - like what vince said, there is no way, very unlike N6600.

icon effects of the theme - possible, though I think this is not what you mean.

what are icon effects of the theme ?

Oh the outer glow and all...