Add html files to the hostname root directory

Hello My hostname is admin.domain.com. When I open it up it shows me the default cPanel defaultwebpage.cgi webpage. Is there any way to upload a html file. I am thinking of a small site with two buttons for the customer, One button with "Login to cPanel" and the other with "Login to Webmail". So in this case if the domain is not yet ready, the customer can still login to Cpanel and I have a general login point. Thanks in advance