The ThinLinc Desktop Customizer is a combination of a web-based administration tool and a command that is run at session startup for all users. It enables the administrator to decide what menu entries should be presented for specific users, and what icons should be made available on the desktop. Which menu entries and/or desktop entries are given to a specific user is decided based on the Linux group memberships of the user, the username and what ThinLinc Profile was choosen (if any).
Since KDE4 uses a different desktop configuration mechanism compared to older versions of KDE, icons added to the desktop using the ThinLinc Desktop Customizer will not be shown in KDE4. This can be solved by changing the Desktop layout setting of your KDE4 desktop to Folder view.