Here are the steps to follow to add an image to the Commissioner’s Note on the main league home page:
Step 1: Download the desired image to your computer/device (right click on the image and choose “Save Image As”)

Step 2: Go to imgur.com and upload the image (look for the + New post button at the top of the page and then drop your image into the resulting window)
Step 3: Right click on the resulting uploaded image and select “Copy Image Address”

Step 4: Paste the copied image address (which should end in .jpg) into the Commissioner’s Note (click Edit Commissioner’s Note to add the image) and click Save

That’s it! If you were able to follow these steps correctly, you should be seeing your image in the Commissioner’s Note.
TIP: If the image you want to add is already uploaded online with an image file ending to the URL — jpg, png or gif — then you can just paste that URL into the note and skip the Imgur steps.
Here are the steps to add an animated gif to the Commissioner’s Note:
Step 1: Locate the desired gif online, right click on it and choose “Copy Image Address”

Step 2: Paste the copied URL into the Commissioner’s Note and click Save

That’s it! Note that if the URL doesn’t end in .gif, follow the steps above for uploading an image to Imgur and copy the resulting URL into the Commissioner’s Note.
And finally, here are the steps to add a video to the Commissioner’s Note:
Step 1: Locate and copy the video share URL

Step 2: Paste the copied URL into the Commissioner’s Note and click Save

That’s it! Note that the video won’t play right in the Commissioner’s Note like it will in a forum post, but it will show an image from the video and link to the destination to play the video.