Although there's no direct way that I'm aware of, you can try to use multiple export View command and assemble the output picture files.
And here's how to do that in Tcl command line.
set cwb [find objects -class cwbWorkBench]
set V [$cwb cget -_layoutView]
$cwb zoomToRectClbk $llx $lly $urx $ury
$V exportView PNG $file
Notice that the "zoomToRectClbk" and "exportView" commands are not documented in the manual. That means they are not officially supported and users should use these commands at own risk.
Thanks for your answer but I am afraid that the result will not be very good for a picture.