I realize this basement needs to be finished but its out of the question, its not my home. So... id like to do what i can for the time being. I am all for buying acoustic treatments if needed, but if i can do some cheap things like a big blanket or some material to block off an are that would be great. The white walls are cement, and the wall the speakers are in front of is thick insulation under a plastic cover so to speak. I also have a boat load of berber carpet i can put wherever.
Without a floor plan, just by those photos, I can't tell much about the shape of your space. But the basic principles of symmetry and treatment apply. With a simple floor plan drawing I could be more specific. The main treatment goals for all rooms are bass trapping and reflection absorption.