The Intro and Skin of FSI Viewer is defined using the INTRO and SKIN parameter.
This is usually set in the _default.xml file, as all FSI Viewer instances use the same skin.
If you like to use a different skin, the easiest way to do this, is to copy the _default.xml configuration file found in your viewer folder and rename it to e.g. _default2.xml
In _default2.xml find the lines defining the intro and skin and change it to the new values.

Next you need to load the new configuration file with FSI Viewer. Append “&defaultcfg=_default2” to your FSI Viewer query. This will load the new _default2.xml instead of the old one, displaying the newly set intro and skin.