WindowBlinds 6.1 was recently released, and one of its new features is the ability to change the background in Windows Explorer. This is a really cool feature, and adds another level of customization to Windows. There are several ways you can customize the Explorer backgrounds. There are over 20 included backgrounds you can change them to, and you can also change the color and opacity.
You can find these options in the "Explorer Backgrounds" tab under the "Look & Feel" section in the WindowBlinds configuration.

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Explorer Backgrounds configuration |
As you see in the screenshot below, you have the Explorer background preview which will show you the changes you make in real-time. The bottom portion of the configuration is divided for the active and inactive backgrounds, but the functions are the same for each.

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Explorer Backgrounds options |
To change to one of the included backgrounds, simply click the box and a list will come up showing the various styles available. Select the one you want, and if no further customization is needed, just hit "apply changes" and the background will apply.

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Change background image |
Using the Hue, Saturation, and Opacity sliders you can further adjust the background image to your liking. If you just want to add transparency then just select the default background. You can see your changes in the preview window, and when you are finished, just apply your changes. Take note that transparency is only available on Windows Vista.

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Change color and opacity |
This is a pretty simple to setup, but has very powerful looking effects. Remember, if you want to get back to the default settings, just click the "reset defaults" button and apply. Here are some examples of how the Explorer backgrounds can look with some of these settings applied.

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Desktop with customized Explorer backgrounds |
You can find more information about WindowBlinds and its other features at the link below.
Link: WindowBlinds