I like Reeder for Mac a lot (the public beta of version 2 is available now) but the icon seems outdated in the dock to me. I made a new icon based on the iOS version of Reeder.
Like the old icon, it has two states, one for when there are no new items:
and one for when you have unread articles:
The icons are available to use; download them here.
All you have to do to use the icons is go to Reeder in the Finder, right-click and choose Show Package Contents. Then, navigate to Contents → Resources and replace the existing icons,
reeder-empty.icns, with the new ones.
The only problem is the icons will revert to the old ones whenever you install a new version of the app.