basement finishing

Hey all,
Hope everyone's doing good!
So, cousin is planning to renovate the basement of her home and change it to a useful space rather than just dumping the waste and unused items in the home. She has started the works of renovation. She has been cleaning the basement. After cleaning she is planning to paint the whole space. She has fixed the stair railing to forged steel bars from an old and broken wooden railing. She also fixed the doors. Well, she is stuck now after as she hasn't quite decided to what actually she should turn this space into. She has a lot of plans for the same. She is thinking of making it into a reading space/library or may be space for her husband to slack around with his video games or like a mini bar where she or her husband can hang out with her friends. She is really confused. My choice would be to change the space into a place where I could party with my friends.
What do you people think about? How would you turn the space into? Any suggestions are welcomed.
Thanks in advance!