Before the cover page was implemented it was possible to have a landing page for visitors who had not 'liked' your page, and a different one for people who hadn't. Is that kind of functionality available with cover images, where people who have already liked the page see a different image from new visitors?
No, this is no longer possible.
It used to be the case that you could set a default landing tab for fans who had not yet Liked your Page, which would change to display different info once they clicked 'Like'. This was frequently used on marketing pages for brands.
However, now the default landing for a Page is always the Timeline, and there is no way to display a different timeline to users based on whether they have Liked the Page. So all visitors who arrive at the Page will see the same main Timeline page.
This article shows how you can edit your Timeline Page to prominently feature a link (in the header and top post) to a custom 'landing' tab you create, which can show different content based on whether the user has Liked or not just as before - but obviously less users will reach this tab than previously when you were able to make it your default.