Widget background images missing on second blog excerpt page

If you look at your browser’s error console, you’ll see the 404 errors for your background images, which will point to where the issue is.

This URL:

../wp-content/themes/themename/images/cat-party.jpg

basically says, “go up one directory from the current directory, then from there look in wp-content, then themes, then images, etc..”.

That works fine on the front page, but when you navigate to /page/2/, the wp-content directory can’t be found by navigating up one directory. It’s looking for your images in:

/page/wp-content/themes/themename/images/cat-party.jpg

which doesn’t exist.

That’s why you need to use absolute or root-relative URLs for assets in WordPress, because you can’t know the context from where your content will be served, so relative links will often fail.