你的图片 URL 应该看起来像 chrome-extension:///image.jpg

Your image URL should look like chrome-extension://<EXTENSION_ID>/image.jpg

您***通过 javascript 替换 css.来自文档:

You would be better off replacing css through javascript. From docs:

//Code for displaying <extensionDir>/images/myimage.png:
var imgURL = chrome.extension.getURL("images/myimage.png");
document.getElementById("someImage").src = imgURL;