I've noticed that emerging the package "tortoisehg" without enabling the "svg" USE flag for all of its dependencies causes the interface not to work properly (missing icons and rendering of various things).
Enabling the svg flag and issuing an emerge --update --newuse --deep world solved the problem.
May I suggest to require such flag in tortoisehg ebuild?
Thanks for reporting.
+ 21 Feb 2013; Mike Gilbert <email@example.com> tortoisehg-2.7.ebuild,
+ Depend on dev-python/PyQt4[svg], bug 458546 by Piergiorgio Beruto. Also add