This Suggestion thread can actually be marked as Completed by a Moderator now.
Here are some associated tips on how to do it, now that the requested feature is implemented and live on the public Roll20:
The following codes now work in the chat & you can put them into Macros:
[This is a link to Google and you can put any words to describe it here inside the brackets](
http://www.google.com)
[This will display a Picture in the chat and you can put descriptive words here in the brackets that show up if the image link is broken](
https://app.roll20.net/images/quantumroll2.png)
So that's pretty cool right? Now check out these macros I created, if you wish to create Macro buttons to make it even easier for posting a Picture or a Link with pop-up dialog boxes in the game...
This helps your Players to post a picture in the chat room using a macro button!
/me describes it so you can imagine this,
?{What is it a picture of? Write a concise caption:|Picture of }
[Image](?{Image URL ending with JPG, GIF, or PNG|
https://app.roll20.net/images/quantumroll2.png})
This helps you post a Hyperlink in the chatroom using a macro button!
/me Posting a web link...
[?{What is it a link to? Write a concise name for the link:|Website Name }](?{Paste Web URL here|
http://roll20.net})