Those names are confusing, aren't they? The names of various system tiddlers in TW LOOK like file paths, but they're not.
There's no directory /core/images/video. If you type (or copy) the text $:/core/images/video into a tiddler and preview it, you will see a link to. If you follow the link, you will come to a tiddler that has a SVG image as its contents.
To get an image into TW, you need to either drag and drop the image into your TW (not recommended except for very small images), or use the [img[]] wikitext or the <$image> widget to refer to images that are external to the TW. There are different ways to do it, and some of them will depend on how your are running TW (as a free-standing file or under node.js). See Tony's prior post for pointers what to do.
-- Mark