Since upstream looks to not want to fix this:
I would like to consider doing this downstream:
"Looks like nautilus doesn't draw desktop icons on Gnome3, that looks reasonable
to me on a system running gnome-shell (as it "replaces" this feature), but this
is not desirable on fallback mode as gnome-panel+metacity doesn't fit these
The reasons provided by upstream to not implement this doesn't convince me at all:
"We want the fallback mode to be as similar to regular gnome3 as we can make it.
Making nautilus run in the one but not the other would contradict that."
From my point of view, even if I agree fallback mode needs to be similar to Gnome3, it cannot be done dropping usability of the fallback mode... and it's clear to me that gnome-panel+metacity don't replace nautilus in any way (while gnome-shell looks to do)
This can be enabled by the user if they want to use it using "gnome-tweak-tool". I guess now we just need to add it to the upgrade guide.
Documented in http://www.gentoo.org/proj/en/desktop/gnome/howtos/gnome-3.2-upgrade.xml