3SpookyChicks nailed it.....check out the Scene Setters. I've used what she mentioned in our unfinished basement and it makes a HUGE impact for very little money.
For an area rug you could pick up a canvas painters drop cloth & paint a pattern on it to replicate a rug. (Just tape down the edges so nobody trips) If the lighting is dim enough and you have enough decor around people won't notice the floors much, so I wouldn't worry a whole lot about that part.
Check out my album, you can see the Scene Setters in the background. If you want I can post more pictures from the previous year that shows the buffet table a little better. Also in those pics you can see a candelier I picked up for $25 at Terry's Village? It's halloween themed with skulls.