I am working on a new app where it is needed to add a busy indicator or progressive bar in the splash screen . It is a hybrid app . So the implementation should in Web resources
In Hybrid applications the ability to control over the splash screen (= change its appearance, duration, and other things like that), is currently not possible in the manner you would like - by using HTML, JS, CSS...
The ability to do so (in Android and iOS only) will be introduced in Worklight 6.2, to be released in June 2014 (this month), where you could decide how and what to display. For example: An animation or a rotating set of images, etc.