Here is a helper to upload a file from a URL directly into your tiddlywiki:
- get this FF addon
- get the URL of e.g. an image you want to upload into your tiddlywiki and do CLR + C
- be sure that the Sidebar and the Tools Tab is open
- click the the icon of the FF addon “upload-file-from-url” and insert the URL by CLR + V
- the URL is added to the import widget and e.g. the image can be imported with an other click here
done 