I was having so much trouble inserting preview images when I was posting my two Harry Potter covers for Game Boy Color on May 29, 2021. When I found out that MediaFire removed the "Direct Link" option, that made me really angry. I even ranted about it in my Game Boy cover post. I looked at Arseen's example. I even looked at my previous cover posts to check the link source. I edited the link source and finally, the preview images came up. I can't tell you how stoked I am! I can sleep better now that I know what to do. I'm going to show you what I did. I made these instructions as simple as I could. I'm going to use my cover of Harry Potter and the Sorcerer's Stone as an example:
First, click "Insert Image"

to get the ["img"] ["/img"] brackets.
Go to MediaFire and click on the options for your file. It's located on the far right and it consists of three vertical dots. Click "Share", and then click "Copy Link". Paste the link here using Ctrl+V on the keyboard. This is the link you will be given:
https://www.mediafire.com/view/ix6vrucaw0z6pj9/GBC_Harry_Potter_and_the_Sorcerer%2527s_Stone_%2528USA%2529_CGC.png/fileTo make a preview image, we need to edit the link. Delete the file name from the link first. This is what you need to get started:
https://www.mediafire.com/view/ix6vrucaw0z6pj9Next, change "view" to "convkey". Add another forward slash with "2db5". You can also use any four letters or numbers you want. At the end of the link, add "6g.jpg". This is what the link should now look like:
https://www.mediafire.com/convkey/2db5/ix6vrucaw0z6pj96g.jpgLast, but not least, put the link in between the ["img"] ["/img"] brackets. Don't use quotation marks inside the brackets. Voila! Now you have a preview image in your forum post. Yay!
If you have any questions, please let me know.
My Covers:
https://app.box.com/s/hote51vbfehfqo0yu5j0