For those with OCD, I have made an Omnifocus 16x16 icon for google reader with no white background. If you have a theme on Google Reader, it will make the Omnifocus Icon look better.
I am hosting it and using this URL:
http://dl.dropbox.com/u/565411/Hoste...F.GR.16x16.png
You are welcome to steal it. I may move the location sometime in the future, so I would recommend hosting it yourself to be safe :).