Interior decorators have painted representations of celestial objects on the ceilings. This is fanciful and probably does not influence the sleep-ability of a room, but designers also know they can influence the mood of a space with color and lighting. It is plausible that a room could be decorated to promote sleep, although we are unaware of any science in this area.
What does your alarm clock do when it goes off in the morning? There are all sorts of alarms and settings. Some people prefer a loud shocking alarm; others prefer gentle music that starts softly and builds. The factors that should go into your decision include how badly you need to get up at a specific time (e.g. to start your morning commute), and how badly you experience sleep inertia
People differ in their sensitivity to light and noise during sleep, but generally the less of each the better.
Light is the major zeitgeiber - the thing that more than any else entrains the body's circadian clock to the world. We are made to sleep at night. That's why you turn out the light when you go to bed. Most people can sleep in low light, but all things being equal, darker is better.
Hospitals, nursing homes, and prisons are notorious in this regard. They never get very dark and facility personnel are present and active all night. It is probably a good idea to avoid turning on the light even when you get up in the middle of the night to use the bathroom.
Many find a formal or informal nightlight useful. They can help you get around if you need to get up during the night and actually are comforting during periodic awakenings into a place that isn't totally dark. There may be ancient origins in the tradition of the nightlife. Primitive people used fires to ward off predators and for heat and and light. Fear of the dark is common and in more dangerous times weas justified.
Occasionally, in upscale (large) houses, the architect segregates the bedrooms from the living area. But it is rare that the materials used to construct those rooms are different or intended to muffle sound. Further, depending on the business of the street and the position of the bedroom, the neighborhood noise could matter. Some people sleep with earplugs and/or facemasks.
Some people sleep better with a white noise in the background. A fan or the house ventilation system sometimes provides this. Crickets chirping in the summer are arguably a form of white noise, but some people get disturbed by them. There are also white noise computer files and programs easily obtained on the internet. Download them to a computer or mp3 player and let them play through the night.
Humidifiers also provide a source of white noise, and increase the humidity in the room. Some people find it more difficult to sleep in dry air – a dry throat bothers them.
"Sleep is the best meditation" - Dalai Lama
Why is it easier to sleep on rainy days? There are likely several factors. The sound of the rain is a white noise. The drop in temperature upon the start of the rain makes it easier. It is darker than before the rain came. The changes in temperature and light level are circadian cues to sleep. Further there is some thought that the electrical charge in the air changes ever so slightly during a rainstorm and that the increased number of negative ions makes it easier to sleep. The science behind this idea is shaky, but it is true that some people experience perceptible feelings before a storm. Rain also cleans the air, leaving a fresher smell, and some people find that makes it easier to sleep.