What Is The Best Way To Spice Up Your Gym Workout?

I'm not sure what you mean by 'spice' up, doing it nude would spice it up for some people!  Do you alternate what you are doing already? Do you have a day for legs, a day for abs and a day for upper body? (Today is my legs day).  If you want to make it a little more hardcore, you can do supersets, where as soon as you finish one set of an exercise, you go straight into another exercise, like a set of press ups.  This is extremely good for you.

Why not speak to the gym instructors, see if they can build you a rotating gym schedule so that you only do the same thing every two weeks, you are still working all the same muscles, but it beats the boredom.

The other thing is, create goals for everything and strive to beat them, a bit of competitive spirit often helps spice things up.