You could add a floor plan as jpegs to your images on VRBO.  If you already have a floor plan, just scan it and convert it to jpeg.  VRBO's image size looks to be big enough to handle that.  I used Photoshop and Dreamweaver to make a floor plan with hot spots that I put on our personal site.  It's interactive such that when you click on a room or area, you will be taken to a page with pictures of that area.  You could also just do a hand drawn floor plan and scan it as a jpeg.  VRBO does allow you to have 2 links on your listing, so you could actually make a whole page for the plan if you have some place to host it.  Here's what mine looks like: ChatterboxToo Interactive Floor Plan . 

Linda