Are there any limitations on the type of page that may be scheduled?

There are no limitations on the scheduling of web pages: you can use .asp, .php, pages etc...
The only ‘restrictions’ are relevant to the fact that the type of page must be supported by the server; for  example, scheduling a .exe file would be pointless as the .exe files does not run on the servers. Furthermore, it is necessary that the scheduled operation does not cause stability problems (or similar) to the machine on which the Hosting service is managed.