This is an excellent idea. Debian is my favorite.
I had to rename galileo-img.gz-1.0 to galileo-img.gz-1.0.gz then gunzip the renamed file and the result had 1024M size.
I then used dd if=galileo-img.gz-1.0 of=/dev/mmcblkX bs=1M conv=fsync and booted on the galileo.
I could ping the galileo. I tried ssh and telnet and couldn't get in.
I put the sdcard in my computer and checked syslog and found the galileo booted the 3.2.0 instead of the 3.8.7 kernel.
This was a good first attempt. Did you intend this to be used with the serial console using the (not an audio) plug or how else do I log in over the network?
Edit: Actually I see where the syslog I viewed was already there in the downloaded image so evidently I never did get this image to boot. Please ignore my comments about the syslog except I still couldn't find ssh or the inet.d for telnet. Maybe you have a newer way to get in if I could get your card to boot. I also tried setting the boot attribute with gdisk and still couldn't boot. I am stumped.