This guide will help you to get a Workshop showcase similar to this:

You need to choose which background you want to use, for this guide, i'm going to be using Stargazer - Shadow in the Trees background.
Once you have chosen your background and bought it, you need to find it in your inventory and click "View Full Size"


After that, you will be on a browser page showing you the background, you just have to save the picture to your computer (or laptop or whatever you use)


and you're almost done, let's move on to step 2!

Alright, so we have the background now, the next thing to do is to save the template below:



great! now we need to use a bit of Photoshop.

open the background with photoshop, then put the image of the template you saved before, it should look like this:

(Make sure the image layer is after the template layer)

All what you have to do next, is to crop the workshop template alone, and you're done!

after that, you'll need to follow this guide:

http://steamproxy.net/sharedfiles/filedetails/?id=727014963

CREDITS FOR THE ORIGINAL CREATORS OF THE GUIDE ABOVE AND THE WORKSHOP SHOWCASE TEMPLATE

Sorry, i do not know who created it to feature thier name.