Yes, you can run a leaderboard style referral program with iRefer. You should choose the Leaderboard template while creating your campaign and then set an end date for your campaign on Initial Setup step.
You can check the Referrals Leaderboard report for the current status of your leaderboard. As of now, we don't show this to your campaign participants, but we do have this feature in our product backlog.
Below is how the leaderboard looks in your campaign report:
We will be adding a new report soon for your campaign participants to view also.