Hi Keith,
There sure are!
In the NT Webserver template, "Settings" -> "Styles" -> "Site", then look for the "Busy Image" field.
You can put your own custom gif / whatever in there.
You can also either use the "Busy Div Class" given, or put in your own, and then in a custom css file change the options for WHERE the busy gif will display.
IE, for one of mine, which is a loading bar, I have:
.nt-busy { float:right; width:126; height:22px; z-index:5000; left: 50%; top: 50%; margin-top: 0px; margin-left: 0px; position:fixed; }
This works for custom popup windows (the z-index).