I haven't posted any images in my blog yet, so it may be the time to fix it:
Solaris 2.6 and Solaris 7 are not very different. Up to 2.6 you can already make such screenshots yourself using the vanilla qemu (git/master). Sneak preview starts here:
For some reason, Solaris 9 looks not that nice:
For all the installations I used a 'PC console' terminal type. Maybe it's not recommended anymore? That's how it looked at the end:
And yes, instead of pressing Return to reboot the qemu machine, I still had to do the following:
echo set scsi_options=0x58 >> /a/etc/system
So, I've achieved the goal I set 7 moths ago. Solaris 9/SPARC will work under qemu.