There is no file upload mechanism on utopian.io yet, yes we can upload images but not files.
As a designer I need to add my source files to my contribution post, for now I have to use/find alternative file servers like my own ftp, or free to use cloud storages. This way my files will stored in 3rd parties. When I'm done with these services, those files are not be able to reachable anymore. Instead of this, if utopian has it's own file management system they will stay forever while post is alive.
And simple file attachment can be evolve in time like redpen.io offers. Which graphic files can be shown, able to comment with pin points for revisions and ideas. Also a versioning can be implemented to show the process of design for other viewers to get opinions about designing.
In graphics section, designers required to upload their source files. They have to do it offsite and link it here. With a file managing system, we can prevent this. This might be useful for other sections, but I'm not involved with them so I can't think of it.
Best Regards.