I've fielded a few concerns around how to access your custom icons in MWS. The documentation around this is sparse, so I thought I'd blog it.
The icons you upload into the Customer Service Site / Microsoft Extranet are stored in your account's root directory. So, in order to access them, you need to set the following lines of code:
myPushpins.IconDataSource = "AccountName.AccountID"
myPushpins.IconName = "IconName"
Where AccountName and AccountID are provided to you by MPNET; IconName is what you named the icon when you uploaded it via CSS. So, if my account name was "Pendleton1999" my account ID is 1999. Let's say I uploaded an icon called "MyIcon" my code would look something like this:
myPushpins.IconDataSource = "Pendleton1999.1999"
myPushpins.IconName = "MyIcon"