You can create a small stairway in a number of ways, but two worthwhile models are the spiral staircase and the modified ladder. A spiral staircase, due to the way it coils on top of itself, takes up very little floor space. Likewise, the modified ladder, which is a stable ladder with big, flat steps, is steep and, so, takes up little floor space. A modified ladder can also be made to fold up or roll against a wall, making it the minimal choice.
You may not have room for a big banister on your small staircase, but add a small railing or at least handholds for safety. Overlap open stair slats so children can't fall between them. Also, if your small staircase is made of a slippery material such as polished wood or vinyl, add traction strips to prevent people from slipping. All of these precautions are necessary for safety, even on a fold-away staircase.
Whether you decorate flamboyantly or subtly or decide against any at all depends on your taste and the particular stairway. Decorating a small staircase can be as simple as adding a small framed artwork to the wall next to it or as complicated as creating decorative storage space for books and bric-a-brac in the stairs. You may want a staircase to disappear into the rest of your home, especially if your home is already crowded. On the other hand, you may want to make a carefully made small staircase stand out as a lovely piece of craft work.
You don't necessarily need a small stairway; there are alternatives. You can use a removable ladder if you don't need to access the other floor very often. You can also build a more substantial stairway outside, if you don't mind having making the trip outside to get to the other floor. For people with a more unconventional lifestyle, creativity adds a lot of character to a home. Install climbing hand- and foot-holds instead of a stairway or a climbing rope.