Amazon (AMZN 1.49%) is aggressively promoting its gateway drug, Amazon Prime, these days. Amazon Prime is the e-commerce giant's loyalty program, which entices customers to boost the value and frequency of purchases on Amazon.com by offering benefits such as free two-day shipping on an unlimited number of deliveries for just a $99 annual membership fee. The company also sweetened the deal for Prime subscribers by adding unlimited video streaming of tens of thousands of movies and TV shows, along with access to over 600,000 books from the Kindle Owners' Lending Library and 1 million songs through Prime Music.

However, if you think you know every there is to know about Amazon Prime, think again. Here are five interesting tidbits.

1. Introducing Prime Photos
Amazon continues to add compelling features and services to its Prime subscription. The latest of these is "Prime Photos," which gives members free unlimited photo storage in Amazon Cloud Drive. The company originally offered this storage perk only to owners of Amazon's Fire devices . But Amazon now hopes that expanding this to all Prime members will attract new subscribers to the program, while also encouraging users to spend more time on Amazon.com.

Source: Amazon. 

"With free unlimited photo storage, we're providing one more reason for members to use Prime every day. Prime has always allowed members to conveniently save time and save money, and now with Prime Photos they can save memories too," said Greg Greeley, vice president for Amazon Prime, in a press release.

2. A rewarding referral program
The world's largest online retailer today counts tens of millions of customers among its Prime members. This is good news for Amazon investors because Prime members spend twice as much as non-Prime shoppers, according to Morningstar. With the all-important holiday shopping season around the corner, Amazon hopes to convert even more consumers into Prime members. That's where the e-tailer's referral program comes into play.

As of September, the company will pay you $5 in Amazon credit for every new customer who signs up for Prime on your referral. Additionally, Amazon will throw $3 in credit your way for each friend you get to sign up for Amazon's Prime 30-day free trial. The customer can then use these credits toward purchases on Amazon.com.

3. Amazon will pay you for patience
The e-tailer will also pay Prime members $1 in content credit when you choose free no-rush shipping. Instead of the free two-day shipping option promised to Prime customers, willing participants will receive their orders in five to seven days. Customers can then use these credits toward books, e-books , and other paid content on Amazon Instant Video.

With the cost of shipping on the rise, this could help the company rein in its delivery expenditures. While Amazon doesn't break down specific shipping expenses, its fulfillment costs climbed more than 29% year over year, to $2.38 billion, in the second quarter.

4. VIP access to sales
Most consumers want to know they are getting a good deal during holiday shopping. Now, Prime members get 30 minutes of early access to select lightning deals on the e-commerce site, as well as early access to daily sales events on MyHabit.com. This should be a big hit ahead of the holidays because customers not only lock in great deals, but they also get to see special promotions before non-Prime members during the busiest shopping period of the year.

5. Free grocery delivery in select areas
Amazon hopes to grab a piece of the $568 billion U.S. grocery market by expanding its Amazon Fresh service. For a limited time, Prime members receive free access to Amazon Fresh in select markets such as Brooklyn and the wider New York metro area. Amazon Fresh provides consumers in certain areas with free same-day and next-day delivery on more than 500,000 products and groceries.

This service typically costs $299 per year, in addition to the annual Prime membership fee. 

These five Prime perks aim to create a memorable shopping experience for members while also attracting new subscribers to Amazon Prime. Ultimately, Prime memberships are one of Amazon's best tools for acquiring new customers and driving repeat sales.