you can easily modify erpnext login page just make a new app copy existing login.html and login.py from frappe/frappe/www/ and paste in custom_app/custom_app/www and add background image or any other design customization
you can easily modify erpnext login page just make a new app copy existing login.html and login.py from frappe/frappe/www/ and paste in custom_app/custom_app/www and add background image or any other design customization