Since October, I have been emailing our registered users with what they like to download on the internet. Users had broad requirements. Many were interested in Christian Orthodoxy, and many liked Cars like Lexus. Some users liked Art preserved in Museums.
I tried my best to add most of the products they recommended. I didn't add illegal/ copyrighted content which could have lowered the life of our website. All of the content added to the website was from Public Domain or CC0 Libraries. We also added a takedown policy such that, potential copyright owners could take down any content they own.
Users loved these Public Domain Images, Movies, and Musical tracks and shared the website with their friends and colleagues. I believe Word of mouth is the most impactful thing that could result in significant user growth. Having active communication helped us reach 500 Registered Users within 3 months. Organic Traffic also played a supportive role in gaining the following accomplishment.