Mixing up my workout!?

I am worried as my routine is basically the same. I do 50 minutes of cardio on either treadmill or elliptical then I do weights. Do I need to switch up my workout? Or is it fine? How can I change it up?? There are about 7 different cardio machines at my gym but they all seem to be the same.... Side note: I only want to exercise at the gym, the weather were I live still isn't warm.