I'm attempting to add my company logo to a visual force page, which is then being rendered as a pdf, but have not been successful.  I've attempted to do so in three ways:

Image is on a website:

<apex:image url="http://www.tsysacquiring.com/graphics/logos/tsysacquiring_top_logo.gif" width="220" height="55"/>

Image has been loaded into Salesforce into documents, and is in the /alva/ folder:
<apex:image value="/alva/TSYS_logo_for_TSYS_Sales_App.jpg" width="220" height="55"/>

Image is on my C:\drive:

<apex:image value="C:\data\TSYS_Logo_for_TSYS_Sales_App.jpg" width="220" height="55"/>

All three attempts have resulted in a broken image icon being displayed.  This seems like a very straightforward thing I'm attempting, and I'd expect it to be rather simple.  Any one have a syntax example that they know works.

Thanks!