Dear frJericho , 

RTE8's file provider is changed for supporting the multiple storage . 

And file url is joined at client side , by 3 parts :

1 - public override string GetUrlPrefix(Storage zone) of the custom EditorFileProvider 

    for example , "/uploads" ,  "/download.ashx?file="

2 - public override string GetUrlPath(FolderID folderid) of the custom EditorFileProvider 

   for example , "/" , "/subfolder/" 

3 - PathItem.Name

   for example "hello.jpg" 

so the full url is  /download.ashx?file=/subfolder/hello.jpg 

If you implement something like download.ashx for it , it need to parse the /subfolder/hello.jpg , and find the real file data to download.

Regards,

Terry