I am a big fan of Quicksilver, I should and have to know how to change my desktop background via Quicksilver.

It's very easy to change your desktop background via Quicksilver. You just need to follow these simple acts.

Act 1. Create Unique Folder Name
The intention of this action is to make Quicksilver easily spots background images with short abbreviation. For example, I made a folder named Custom to store all my background images. With this, Quicksilver only needs search-term cust to locate this folder.

Act 2. Set Convenient View
Convenient view here means images can be viewed without doing more effort on opening it with other image viewer. Mac OS X supports this feature. Open with Finder the images location, press J to call up View Options. Move the Icon Size slider to right size until it's large enough (I use 120x120) and tick the Show Icon Preview checkbox. With this, the images can be seen conveniently.

Act 3. Pass the Image to Quicksilver
Highlight most favorite image. To pass it to Quicksilver, keystrokes can be used.

Act 4. Change Quicksilver Action
Quicksilver default action is open file, it's needed to be changed into Set Desktop Picture, it always works well for me with abbreviations setpict.

Act 5. Relax and Enjoy
Hit to execute Quicksilver action. Actually you can press F11 to hide all applications window and enjoy your brand new background image before going back to your works.