If you want to avoid scents, then be sure to study up a little bit on color symbolism because you're going to be setting your scene that way instead of with aromas. Also studying a bit on symbolism might be a good thing, too. Sound is also good for setting a mood. Music softly playing in the background might help. I like how nisaba has used the dark with the light, cobwebby effect on her table.
As for myself, I don't do anything really spectacular. I have a pretty Halloweenish tablecloth that's primarily orange with black bats printed on it that's great for Halloween. To go with it, I have a wonderful big bag with Halloween print that coordinates to the table cloth and it's big enough to hold a Halloween tarot deck, a Bohemian Gothic regular, a Bohemian Gothic silver, and my beloved VR Gold as well as the tablecloth when it's not in use. The table cloth is big enough to fit my medium sized round dining table, so I put that on and just sit the bag full of decks on the table. In the middle of the table I have a selection of little colorful pumpkins and gourds in a spiderweb wire basket with a wire spider on the side and that's an October Halloween decoration for whether I'm reading for friends and family, for Halloween night free readings for neighbors or to sit and have coffee plus it's really nice for the season in general. I can add a big fat candle or a cluster of small ones for Halloween night readings to add atmosphere and move the basket of stuff out of the way for the readings.
Aside from all that, I just figure my deck and me is enough. (Just noticed I left that sentence hanging and posted the post. Criminy! What was I {not} thinking? ) I don't usually do anything else except just spread out the cards and read them.