Image Show GK4 is proppably a good solution for You, but it doesnt work with images in folder - You have to specify each "slide" and upload image to it. Also it doesnt have typical lightbox effect, but check it out in our demo - it is used in first "screen" of intro - and on one of the slides there is set backgound.
To configure menu You need to edit Main Menu (not Main Menu - subpages) - and to get correct anchor, You would need to use some kind of firebug or chrome developer tools to find right element id to create anchor to it.
If You have problem with anchor thing, and would need a little help - show me your site's url, tell me where You would like to link (or better - attach screenshot with marked place) and I'll write all needed anchor elements.