You can customize the new Activity Stream page by clicking the gear / wheel icon in the top right corner of the page.

Are you talking about the default about:home or the New Tab page? I'll give you the options to disable both if you wish to.

For about:home, go to about:config using Firefox's awesomebar and click the button to continue on. Search for this pref using the search bar provided (browser.newtabpage.activity-stream.aboutHome.enabled) and double click that so its status is set to modified and its value false.

For the new tab page, you can do the same above except use this pref: browser.newtabpage.activity-stream.enabled

Thanks for the reply. I miss an option to display the firefox logo on about:home to get a look similar to pre-quantum/photon versions. For new tabs I also use about:home... I know there is this about:logo but it doesn't look good.

You could try this:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk.

(2) In the search box above the list, type or paste newt and pause while the list is filtered

(3) If the browser.newtabpage.activity-stream.aboutHome.enabled preference is true, double-click it to switch the value to false

Okay, I didn't think that this would solve it but it does. I thought it would just hide top-sites or highlights... Thank you very much to both of you!