There really isn't a way to do this. (I know that SiteScape Forum allowed you to do this, but that approach was not added to ICEcore.) You can achieve much the same results by adding the images to the entry descrption as "inline images". But this doesn't help you if you are trying to attach an html file. You might also try adding sub-folders under your current folder to hold the files referenced by your html file. This will probably work, but only when you are viewing the folder as a WebDAV folder.

Sorry, there really is no good answer to this.

I do think that this is a key requirement for a system that offers Document Management features.  (As far as I know, more than 33% of the SiteScape forum users use it for Document Management.)

I have a SiteScape customer planning to use ICEcore Enterprise as a repository for policies and practices, and this limitation poses a serious problem because most of his policies and practices are in NetHelp format (the HTML4 compatible electronic manual format produced with the tool called Doc-to-Help)

Now all I need is the time to do it. No commitments on this being added. But I'll add it to my list.