You can change them out, but you have to take the whole fixture off the ceiling for that to work, and you have only removed the glass.

I can't stand boob lights, either.

The "base" is the JUNCTION BOX and electrical attachment. The entire "decorative" fixture must first be removed, and a new one/your selection wired in. The "box" underneath your hideous fixture is a mere five inches wide in diameter, can be covered with any incandescent flush mount selection. Your "rental" implies asking permission, responsibility for safe installation and wiring, and replacing to original when you depart. Ask the landlord is my advice........or get a QUALIFIED licensed electrician and take your chances he likes the improvement.

Thanks for the replies! Seems like I'll have to remove the decorative fixture as well. @Jan Moyer Thanks for the landlord details, I'm aware I'll have to replace the old fixtures when I move out. I'm also aware of the safe installation.