I'd say the patch speaks for itself.
Created attachment 144967 [details, diff] eutils.eclass.diff
Dude, this needs to go in pronto. Every .desktop file created with eutils is invalid because of the icon-name.png stuff. The extension is absolutely not allowed, so it needs to get punted from the eclass.
Created attachment 220903 [details, diff] New patch Here is a cleaner patch that does about the same thing.
http://sources.gentoo.org/eclass/eutils.eclass?r1=1.335&r2=1.336