Update
Currently using Firefox 61.0.1, the old methods no longer exist/work. Now you can either add them manually or use Highlights.
If you choose to use Top Sites, you can add your own sites, pin them, and dismiss the ones you don't want to see.
You can also set the number of rows you want (1 or 2 rows) in Firefox's options.
For Highlights, you can just have Bookmarks checked but it will only update once you add new bookmarks. It will not pull any old bookmarks so you'll have to add them again.

Outdated
Yes, you can do this.
You can either change the new tab page itself
You can set the value of the pref browser.newtab.url using about:config to
chrome://browser/content/bookmarks/bookmarksPanel.xul
or
Drag the bookmarks you want to the tiles.