Hi,
I know that there are plans to integrate the Activity Stream in Firefox 56. I have a few “personal blockers” that needs to be addressed so that I won’t use my own add-on New Tab Override to replace the new tab page. In general I like the activity stream. 
Most important: A solution for HiDPI displays. Most Favicons in the activity stream are very blurry on my MacBook Pro with Retina display. The same applies for some of the “big images” in the highlights.
I know, it’s difficult if a website does not provide high resolution assets, but there needs to be a solution, because I see this page a few hundred or thousand times per day, so the status quo of the activity stream is not a option, it’s too ugly for daily use with all the blurry images.
I like on the current about:newtab page that I don’t have to scroll. There is enough space for the row of top sites and three highlights. But for more I have to scroll. I would like if I could limit the number of highlights so that there is no scrollbar.
Similar, I want to limit the number of top sites. There are already browser.newtabpage.columns and browser.newtabpage.rows in about:config. It would be great if these preferences could be respected. It would also be okay to introduce new settings. I don’t need visible preferences, about:config is okay.
And of course: I want to customize the pages. That’s really a blocker for me. But according to https://wiki.mozilla.org/Firefox/Activity_Stream_1.0 it seems to be a planned feauture.
