So, I started a series of original wallpapers which I want to share with you.
Click on the links below the thumbnails to download:

Normal: 1600x1200 px, 1024x768 px
Widescreen: 1680x1050 px, 1280x800 px

Normal: 1600x1200 px; 1024x768 px
Widescreen: 1680x1050 px, 1280x800 px

Normal: 1600x1200 px; 1024x768 px
Widescreen: 1680x1050 px, 1280x800 px

Normal: 1600x1200 px; 1024x768 px
Widescreen: 1680x1050 px, 1280x800 px

Normal: 1600x1200 px; 1024x768 px
Widescreen: 1680x1050 px, 1280x800 px
These wallpapers were created in Paint.NET, which is an excellent free Image Editor. Except the Monkey logo, of course, all graphical elements were made from scratch using it.
I'm releasing the original layered hi-res file, with plenty of resources for you to play with layers, transparency, recoloring and so on... Just install Paint.NET, download this PDN file (3.95 MB) and go create your own custom MM3 wallpaper!
Desktop Visual Style
The Zune team has developed an official XP Visual Style that matches these wallpapers and Glided skin very well.
See a screenshot:

I found it via this link.
And here is direct download link.
It comes in an MSI install package. Just download, them double click the file to install.
Notes:
- I won't be releasing these wallpapers in other resolutions. There are four different screen formats already. Besides, you can download the hi-res version and resize it to any desired resolution using Paint.NET.
- I won't be releasing these wallpapers in other file formats. You can download the hi-res version and covert it to different formats using Paint.NET.
- I won't be accepting requests to make slightly different versions (I mean alternative elements placement, no text, darker versions, brighter versions, etc). Guess what... you can download the hi-res version and customize it using Paint.NET!
Got the idea? So enjoy!
Important note 1: Thanks rusty for letting me use the Monkey logo.
Important note 2: The "Dancing Monkey with iPod" is a mod by me. MediaMonkey developers have nothing to do with it.
Important note 3: No monkeys were harmed during the production of these wallpapers.

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12-08-2007 - Update:
- Added Wallpaper #5 and updated layered PDN file.