Hello Gigi,
The websites in your examples seem to have a movieclip where everything is
included (you can see that really good on jlern.com). However the movieclip in
jlern.com doesn't include photos which makes the movie smaller.
If I were you I would load the images of the different "pages" at the moment
the visitor clicks on a button to see a page. You see that akqa.com does the
same. Everytime you click on a button you see that it needs to load for a
little bit.