The chances that your Company, like ours, is going to want to upload documents to SharePoint 2010 that are not recognised by SharePoint out of the box and show the generic “blank document” style icon. Fear Not! It’s relatively simple to add an icon for a certain file type – PDF’s for example. These steps will need to be repeated on each WFE server in your SharePoint farm.
First thing you are going to want to do is get an icon for PDF files, or any other file type for that matter. (The icon for PDF’s can be found here)
Then head on over to C:/Program Files/Common Files/Microsoft Shared/Web Server Extensions/14/TEMPLATE/IMAGES/ on your SharePoint server and place the downloaded icon there.
Once this is done open C:/Program Files/Common Files/Microsoft Shared/Web Server Extensions/14/TEMPLATE/XML/DOCICON.xml in notepad or something similar. Remember to make a backup of this file before you modify it incase everything goes Pete Tong!
Look for the lines in the file that start “<Mapping Key=” and add <Mapping Key=”pdf” Value=”pdficon_small.gif”> on its own line. Save the file when you are done.
Now depending on your maintenance schedule you need to restart IIS for this change to take effect. If you don’t have a certain maintenance window then go ahead and open an elevated command prompt and type IISRESET. A system restart would also do the trick.
Once either the service has restarted, or your server is back up from that long reboot while the RAID card initiates, browse to one of your SharePoint sites and upload a PDF. Simple.
Of course this method can be used for any file type you like by simply substituting Key=”pdf” with Key=”<File Extension>” and Value=”pdfIcon_small.giz” with Value=”<Icon_Path.jpg>”. Don’t forget that most web browsers will not render a .ico file though!
Dan McIntyre 
