Is it legal for me to download images that have no explicit rights or licenses? For example, from a website that has art but there is no "licensed under" copyright notice or it's "All Rights reserved". If it's "all rights reserved", I can't download it on my computer? Even if it's just for personal use as a wallpaper or to keep on my art folder because I like the art, and also it would also be illegal to share that image with others?

This is also why I have been hesitant against downloading any image from the booru because they all are copyrighted, except the CC ones, which is why all my soyjaks are obtained from the wiki which is public domain
>Picrel is CC0