You'll enter into a directory presenting the original images uploaded into IA. They are jpg's (first trouble; tiff will be better) and they have a decent resolution but a very low contrast. Standard djvu compression can't give a good result. You could obtain something better building a uncompressed "picture quality" djvu, then loading inside the IA text layer with DjvuLibre, But I think that it's very difficult to obtain very good djvu. 

Alex