How to Add / Size the Logo and Favicon in Google Sites
How to Add a Logo and the Proper Dimensions for the Image
There are two ways to access the logo and favicon image upload options: Site Settings and Custom Theme > Images
Go to the general site settings
Select Brand Images
Upload a .jpg .gif .png image as your logo
Tips for Logo Sizing
The displayed maximum dimensions for a logo are: 225 pixels wide, 40 pixels high (225x40), that is a 5.625:1 ratio. I recommend working in multiples of 40 for a clear image. Keep in mind the logo image will also be displayed on social media as the default site image or thumbnail. So for instance, my logo is 450x80 pixels. Don't forget to add alt text for the logo as part of good SEO practices.
Accessing via Custom Theme Options
Go to Themes
Edit Custom Theme
Select Images
Upload a Logo image to your theme
View different examples of logos used on Google Sites websites
How to Add a Favicon to Your Google Sites Website (Browser Tab Icon)
Just like the logo, there are two ways to access the favicon image upload options: Site Settings and Custom Theme > Images
Go to the general site settings
Select Brand Images
Upload a .jpg or if you want transparency, .gif or .png
We recommend 48x48 pixels image, but you may try multiples of 48 like 48x48, 96x96
Official Source: https://developers.google.com/search/docs/appearance/favicon-in-search
Common Issue: My Favicon is not displaying on Google Search
From trial and error research we found a 48x48 .png image uploaded to the custom theme > images > favicon settings works and should be displayed with your site search result listing when your site is recrawled. Request Google to Recrawl your Home Page when you upload a new favicon. To request recrawling your site use the Google Search Console's URL Inspect Tool on the homepage. If you are not using a custom theme on your site, then do so at the Site Settings > Brand Images area.
Note: Google Sites does not support .ico images as the Icon nor .svg
Common Problem: The Logo is Too Small for My Site
If you use the top navigation logo image spot for your logo then you are constrained to the above dimensions. This logo is optional, so maybe don't upload it here if you will run into legibility or clarity issues. Add your logo to the landing page header instead and use Spacers to position it well. Keep in mind the 12 grid system of Google Sites webpage layout.
