if you don't mind getting your hands dirty, data.img is just an ext2 partition in a file. you can mount it as a loop device either from within android or from a suitable linux computer.
Code:
su
mkdir -p /mnt/data
mount -o loop /sdcard/andboot/data.img.old /mnt/data
I don't know if these precise commands work, but that's the idea.
Once you've done that, you've got to find where the SMSes are stored... unfortunately, I don't know where that is. Almost surely somewhere under /data/data (which'd be /mnt/data/data if you did it the way I typed up there). Titanium Backup suggests that it's in Dialer settings, but I haven't got my phone nearby to check on that.
That's as far as I can lead you. Good luck.