When you create a new Google Sites, it is automatically saved to your Google Drive. Yes, your entire website in Google is treated as a file and can be shared just like other documents that are found on google drive.
Google Sites has no storage limit, and Drive doesn't count any storage. So you can upload as many images or text to your Google Site as you like without worrying about it consuming your Drive space.
You should also take into account where your images are stored, and be able to export them when revision is needed.
When uploading images in Google Sites you need to consider the pros and cons that come with these three options.
Option 1. Add images from your computer to Google Sites.
You can upload any number of files within your Google Sites and it will not count towards storage in your Drive. To upload images to your site, go to ‘Insert’ pane on the right side of Google Sites editing page. From there you can select "Images" > "Upload" and select file from your computer.
PROS: You won't have to worry about storage.
CONS: Hard to locate uploaded files. You may use the "Save Image As" option to download some of the images. However, if you want to extract a background image from your photo, that function does not exist and will be difficult to locate.