Add maxWidth, minWidth, maxHeight and minHeight options that takes a value or function that returns a value and sets it with ".css('max-width', value)" on the overlay element every time it is shown.
Fix the "hidden" option so it just calls ".hide()" on the overlay element instead of running the "show" and "hide" methods.
Add "modalClassName" options, whose value is set on the modal mask element if options "modal" is true and "modalEl" is not a jQuery instance.
Hide modal mask element on plugin instantiation if option "hidden" is true.
Add "beforeShow" and "beforeHide" options which take functions that are run before the "show/hide" methods. If the functions return false the "show/hide" methods will be aborted.