Login to the control panel of your main domain NOT WHM
click on file manager
top main links --- click on 'up one level'
double click or open the folder cpanel3-skel
double click or open the folder public_html
Now you can put your either index.html or index.php there
TIPS: To avoid cluttering new accounts with photos etc , just put the index file and link the photos from somewhere else in your real webspace of your main account ---if you want to decorate the default page with graphics.
Now every new account will automatically have this page.
