<texcode>
\setupbackgrounds [page] [background=mybg]
% switch it off again:
\setupbackgrounds [page] [background=]
</texcode>
You could also typeset the layer once using <cmd>placelayer</cmd> or <cmd>flushlayer</cmd>, but then the location depends from the upper left of the text area! (Bug?)
* switch off backgrounds: <code>\setupbackgrounds[page][background=]</code>
* add a background: <code>\setupbackgrounds[page][background={\currentvalue, mylayer}]</code>
==Placement==