Made this tutorial long ago: [link] (Create an envelope icon in photoshop) byAsher Abbasi at PSD tuts+. After doing it I kept the .PSD in my hard drive, well; I decided to re-do everything and create a new envelope from this; and also and release some of the old WIPs I had on my "projects" folder.
This is not very impactacting, but I think is fine, at least is better than my first icon. The making of an icon is harder than making a dock, but right now I find it more interesting.
The pack contains .ico files (Windows) .icns (Macintosh) and PNG (Linux) files.