Jealous! I hope it turns out fantastically.
Some thoughts:
- I'd really encourage using scent in the room, preferably the same scent every time so it just becomes 'part' of the room. The sense of smell is so critical for getting behind the conscious brain, especially when it's the same every time. If incense doesn't work for you or the people you're reading for, try essential oils; other than the heavy florals, most people are able to tolerate essential oils well. In terms of scents, some traditional divination incenses/oils are sandalwood, cedarwood, rose (can be too much for some people), dragon's blood, and frankincense.
- Speaking of traditional divination herbs, I know I'd want supplies for making divination tea! Blend together dried hibiscus (don't use too much, it's strong), cinnamon stick, food-grade dried rose petals, dried orange peel, lemon balm, and black or green tea, to taste. Put it in a decorative jar. Get yourself a pretty tea pot with a built-in tea diffuser, plus two mugs, and an electric kettle - you're gold.
- If you have a source of natural light, plants are always a good thing in divination spaces. Bay, ivy and fig are all traditional and make good houseplants, but any plants will work (and will keep it from feeling too b-movie, as previously mentioned).
- Don't forget creature comforts; if you're comfortable in a space, you're more likely to spend time there (and more likely to be able to focus). Comfortable chairs, good lighting sources for different moods, something to wear or drape over your lap if you get cold, something to nibble if you get hungry (a small jar of nuts will do it) - all of those things will make the space more attractive to be in.
- If you plan on burning candles and incense, make sure to be fire-safe. Lanterns for tea-lights or pillar candles are pretty and reduce the risk, and for incense my favourite trick is to buy a gorgeous ceramic tile from a tile or building store and use that to rest my incense burner on. Inexpensive, beautiful, and you can get a reasonably large one which will make sure that any still-smoldering incense that drops won't end up on something flammable.
Sorry for the mini essay!