I have never had any issues with spaces in filenames, although there certainly may be client devices that would. The default SSID that the system designates when you build a librarybox has spaces in it, so that as well is nothing I've seen issues with.
I can imagine a situation where a client wouldn't like it, but from the server-side, LibraryBox is fine with spaces. There are some font encodings and alphabets that cause it issues...we had a problem with Tibetan, for instance. But spaces? Spaces aren't a problem.
Jason