Hi, I just did a quick experiment on the about:newtab page and removed some of the tiles. It looks like it just adds new ones. Clearing the cache could start fresh for the top sites, however you mentioned you already tried this.

Deleteing the places.sqlite file will delete all history and bookmarks (you can export your bookmarks from the bookmarks manager before you do this for back up) and check out the newtab page (it should be blank)

Do you mean to pin specific websites to tiles or do you want to use a thumbnail of your choice for each tile regardless of what Firefox generates from the cache?

I have my bookmarks pinned to the top 9 sites,and I'd like to change how the square looks,for example,I've pinned a facebook page and I'd like to add a custom picture instead of facebook login page

Try this extension:

• Customize about:newtab: https://addons.mozilla.org/firefox/addon/customize-aboutnewtab/

I want to change the icons,not the background

Sorry, I posted the link to the wrong extension.

Use this one instead:

• New Tab Tools: https://addons.mozilla.org/firefox/addon/new-tab-tools/

There is a tools button in the top right corner to access the new tab page settings.

this actually works! thank you so much!!!