Sometimes websites won't let you load images without a valid referrer. Take this as an example, it returns a forbidden error. In a similar question I have found this answer, that suggests doing something like this:
<img src onerror="fetch('https://i.pximg.net/img-original/img/2020/11/28/06/04/23/85949640_p0.png', {headers: {Referer: 'https://www.pixiv.net/en/'}}).then(r=>r.blob()).then(d=> this.src=window.URL.createObjectURL(d));" />
This however, still fails to load the image. Checking the code of some extensions that promise to fix this error by installing scripts shows that they're just changing the referral, and that this should get things working.