I was tinkering in that space in the mid-90s, and always felt the file format was a missed opportunity, and wasn't taking any of the lessons of HTML.

What I wanted (but never built) was a semantic file format, something like:

    <room style="square" id="room1">
      <wall direction=north>
        <picture frame="modern" src="http://foo.com/fancycat.jpg" />
      </wall>
      <wall direction=south>
        <door room="room2" />
      </wall>
    </room>