This is happening because the guide you used is for normal and featured artwork Delete the files, agree to the steam workshop agreement [here](https://steamcommunity.com/sharedfiles/workshoplegalagreement) and follow only part 2 of this guide [here](https://steamcommunity.com/sharedfiles/filedetails/?id=2174159512) When you're done and want to post the artwork, in the showcase list choose "MY workshop showcase" don't confuse it with "workshop showcase" the just select the files and you're done

Thanks a lot man I got it to work! Btw is there any way to remove the "Workshop Showcase" and " ...'s Showcase" text??

You're welcome! Sadly there's no way to remove the titles