is it possible to alter or extend existing backend admin login page ?

[adrianmak]

Instead of creating new login form with new url, could i alter or extend existing backend admin login page ?

Like apply more styping, say put a company logo.Add recaptcha on the form.

[Ivan Gretsky]

You can create your own admin theme or just add some css/js with Admin Custom Files module.

You can completely replace or hook into ProcessLogin module. But why do you need it?