Let's be honest, we all like to play a bit and customise our experience. In particular if it is for an application we use everyday like OmniFocus. In the current Mac version you can achieve this using Themes and Perspectives. When you build a new Perspective you are typically looking for a suitable icon to go with it and to display in your toolbar. Ideally you would like to use a consistent icon set for this. Below are four beautiful designed sets that allow you to do exactly that.
Joseph Wain has created a great icon set originally targeted at iOS developers, but Glyphish also makes awesome Perspective icons for OmniFocus. It ships free with 200 icons unless you aim for retina icon resolution and another 200 icons more which requires you to put down 25 US$ (which still is not much). The vast choice of symbols should not leave any Perspective uncovered.
Icons & Coffee
This set has been designed specifically for the use as OmniFocus Perspective icons. With this special purpose in mind, designer Silvia Gatta crafted each one of them to perfectly fit the typical requirements of OmniFocus users. The Icons & Coffee OmniFocus Perspective set includes 50 retina-ready icons and is available for 9.99 US$.
A slightly older set, which may be recognisable by the design patterns used to create it, comes free and features 170 icons providing a pretty comprehensive choice. No matter how odd your Perspective is the WooCons set will have you covered with a nice picture for it. Unfortunately the icons are 32x32 pixel which makes them a little blurry on Retina Macs and iOS devices.
My currently favourite 0 US$ set. The round shape and pattern language may not be everyone's favourite, but for me they look rather beautiful in my toolbar on Mac OS X and on my iOS versions of OmniFocus. I have yet to come across a perspective I built that does not find a corresponding icon in Stylistica. I also used the set for the slides supporting my talk at the OmniFocus Setup event earlier this.
Find the icon set that works best for you and makes OmniFocus not only a productive but also a visual joy to use. Remember that perspective icons sync across to your iOS versions as well. Just do not end up spending half a day finding the perfect icon set instead of doing the real stuff!