This should be really easy in Construct 2. What is making you say it's impossible?
Just make a layout per page, and put a new Sprite object on each layout with that page's image. Done!
I don't know why people are talking about tiled backgrounds - there's no particular technical difference, other than that in some cases they can display with reduced quality in WebGL mode if they are not a power of two size, which is a pretty good reason to use Sprites instead.
Providing you use separate Sprite objects, and not animation frames all in a single object, Construct 2 will manage the memory of each page's image for you. In WebGL mode, changing page will deallocate the previous page's image then allocate the next page, keeping memory use down. In canvas2d the browser should at least do something vaguely reasonable, such as start deallocating old images when memory use is getting high. CocoonJS is currently unsuitable for this though since it has no memory management, and I keep trying to get them to support it, but they're not answering my emails right now.
So, have you tried this? It should work fine in a browser.