If booting with:

kvm [...] -hda /grml/test.img -kernel linux26 -initrd initrd.gz \
  -append "boot=live findiso=/foobar/grml.iso"

it works fine, though with:

  kvm [...] -hda /grml/test.img -boot d -cdrom ./grml.iso -boot d

and "findiso=/foobar/grml.iso" as additional bootoption the CD-ROM is used 
instead of the ISO from the harddisk. We might have to prepare the findiso 
handling in live-premount/ already instead of live-bottom/05mountpoints  so the 
(non-specified) boot medium does not win over the specified harddisk file.