At the moment Retrospring has 2208 users but I see less than 50 active users. Why do you think so many users decided to stop using the site?
Don't be fooled. Despite making up 99% of throwaway accounts, only 1 salty anon is responsible for the bulk.
On a more serious note, yeah, lack of features. It's understandable tough, serving media is e x p e n s i v e.
Tough integrating your thrid party favourite, like imgur or federated software would be a choice solution here.
Basically some bb-codes to embed certain media. Links are a good way to do that right now, maybe using a client side script to enhance the experience would be an intermediate solution? tough you gotta trust your sources :)
Retrospring uses Markdown for formatting
*italic text*
for italic text
**bold text**
for bold text
[link](https://example.com)
for link