I think there should be a BBCode tag that takes the thumbnail if a project and displays it as an image in the forums. It would be like this
Wouldn't that be useful for showing the image of your project in the Show and Tell forums?

That's a good idea.

You can already do that sort of thing. All you need is the project ID, which is the numbers at the end of the URL. Then just enter [img]cdn.scratch.mit.edu/static/site//projects/thumbnails/xxxx/xxxx.png[/img], in which the x's are the project ID, but separated into half and half, same order.

For example, project ID 10738584 would look like this: