You will always want to think about how long you have to let the candle burn safely before you have to extinguish it for bedtime or because you have to leave the house. This is especially true with candles of greater mass and circumference, because extinguishing these before they have liquefied evenly all the way to the outer edge can ruin their future performance. This can take up to five hours in some cases.
For baths and relaxation sessions, most people prefer a mild to o scent candle, as the bathroom is a smaller space with less ventilation, especially when steamy air is involved. Also, here is a great place to use votives and tea lights, as they will usually be ready for extinguishing within an hour of being lit. Larger tapers and pillars can also be used, as long as they are on a secure, safe, hardened surface and surround so that you can leave them burning with less worry. You should supervise all candles while they are lit.
Most suggest that whites and creams work best for creating romantic surroundings, and this tends to be the case. If you choose to go darker, turn to the opposite end of the spectrum with deep reds, grays, and black. Candle tins offer a greatly secure and stable source of candlelight for use in groupings.
Regardless of the style of candles that you choose, try experimenting with their placement around the room, safely of course. Your favorite candles could be even better than you imagined when staged on lowered tables or cleared book shelves. The more height and variety you can manage, the more eclectic and magical your candle experiences can become.