Remember more isn't always better. If you feel you need to switch it up, change the exercises IMO. For example, substitute your squats with front squats. You could even change your rep range, and number of sets, rest time, etc. There are a number of different things.
How many sets do you do now? What is your rep range like?
You could do something like this, I like 6-10 rep range for compound movements. 10-12 for isolation exercises
Front Squats 4 sets
Hack Squat OR Leg Press 3 or 4 sets, if you can do it or want to
Leg Extension 3 or 4 sets of 10-12 (really squeeze at the top)
Romanian Deadlift 3 or 4 sets OR Good Mornings OR Glute-Ham Raises
Leg Curl or Lunges 3sets
There really is no end, you could do so many different things. Pick the ones you like and we can get more specific.
Some more hamstring exercises are Glute-Ham raises or Good mornings. Just google them, you should be able to find a video or description of the exercise. If not, let me know I can explain.
This is just a quick job of trying to help you out. If you see something you don't like you can always change it, experiment with new things. You'll find what works for you.
__________________ Strength is understanding that your power is both physical and emotional. - Henry Rollins | 
”A man can fail many times, but he isn't a failure until he gives up.”