Currently, if you have a PNG or JPG for example, and want to upload it into WebGPU, you must upload through an ImageBitmap (... or a canvas, technically). The basic set of ways to upload are:

• HTMLImageElement -> createImageBitmap -> copyExternalImageToTexture
  (Note image.decode is not useful here, because createImageBitmap is already asynchronous, and already expresses the intent that the image must be decoded.)
• fetch -> blob -> createImageBitmap -> copyExternalImageToTexture

The core problem is, it's impossible to express the full intent of "I have a URL for an image and I want to copy it into a GPUTexture". The createImageBitmap step in particular cannot know that the goal is to copy the image into a GPUTexture and then throw it away and never use it again, so there's no real way to avoid an extra copy in the middle.