If you want to add a link in an XML file, then you have to check the strings used by the application. Typically, there should be a standard code section that you can use to define the image stored on the webserver or on another Internet address.
Firstly, check the Help section provided on Stalker. Simply search logo into the Help section to see all the available date.
Additionally, look in the installation directory for Help guides or manuals related to Stalker.
Unfortunately, this is the only thing I could find for this inquiry.