Yes you can! WebinarIgnition offers you many options for customisation. The first set of options allow you to customise Webinarignition's pages themselves, and the other set of options (available in the Ultimate version) offers many shortcodes you can use on pages you have designed yourself.
Customising WebinarIgnition's templates directly
WebinarIgnition comes with four templates: the Registration, Thank You, Countdown, Webinar, and Replay templates. Each of these offer some degree of customisation. You can, for example, set a banner and background colour for the Webinar page.
Customisation with shortcodes
The second set of customisation options offer many shortcodes that you can paste in any wordpress page you like. There are shortcodes for
the Registration, Thank You, Webinar, Countdown, Replay, and Closed pages. Check out the video below for an overview on how flexible WebinarIgnition customisation options are.