Adding custom icons for the media library

If you need to have some custom icons in the media library you have several options:

• Install the corresponding program on the computer and associate the file with this program (ie: acrobat reader for .pdf files). This option is maybe not an option for the production server.
• Associate the file extension in the operating system. Open "Control Panel -> Folder Options-> File Types -> New -> Add file Extension" then register the icon for this extension (Advanced -> Change Icon)
• Associate the Icon with the file extension in your web.config. Add thumbnails generator for the known file type. For example for PDF file type:
  

  <mediaType name="PDF file" extensions="pdf">
    <mimeType>application/pdf</mimeType>
    <forceDownload>false</forceDownload>
    <sharedTemplate>system/media/unversioned/pdf</sharedTemplate>
    <versionedTemplate>system/media/versioned/pdf</versionedTemplate>
    <thumbnails>
      <generator type="Sitecore.Resources.Media.MediaThumbnailGenerator, Sitecore.Kernel">
        <extension>png</extension>
      </generator>
      <staticFile>Path where the icon is located. For example /sitecore/shell/Themes/standard/images/pdf_icon.png</staticFile>
    </thumbnails>
  </mediaType>
  

After these modification, clear the cached files:

1. Open the folder "/Temp" under the Sitecore root.
2. Delete all files with the name "fileicon.....".
3. Clear media cache "/App_Data/MediaCache" under the Sitecore root.