Changing the lighting would be one of the first things.

Then you could add wainscoting or at least baseboards and horizontal top trim and vertical corner trim to help hide wires to ensure have outlets where you want/need them.

On the wall on the end of the room where it is likely you will hang a tv, adding a row of floor-to-ceiling (shallow) built-ins for tv and gaming items is worth considering. Having cabinet doors below can give you a place to hide things you don't want to display while open shelves above can give you options for displaying family treasures and mementos -- perhaps even a few family photographs.

If the floor is smooth level concrete, you could leave it as is or paint it darker rather than adding other flooring -- just depends upon where you most want to invest your budget.

https://www.houzz.com/magazine/how-to-get-that-built-in-media-wall-you-really-want-stsetivw-vs~21828581