Here's how you can see more Top Sites in Safari 7 for OS X Mavericks by increasing the number displayed by default.
1. Open Safari 7.
2. Go to Preferences.
3. Go to General.
4. Click the "Top Sites shows:" dropdown menu.
5. Choose 6, 12 or 24 from the available options.
Personally, I prefer the 24 option as I like to see the most Top Sites possible. It just makes it easier and faster to go to your usual sites when you open a new browser window or tab.
The new Top Sites interface, accessible by selecting the Top Sites icon in the favourites bar, presents you with six, 12 or 24 of your favourite sites in a grid.More at Macworld
Additional resources for Safari