Ok cracked the code for you...

The bug is that it will NOT accept JPGs, you have to submit a PNG file. AND you have to shrink it way down. When I converted it to PNG it was 2 megs, I had to shrink that down to 1 meg to get it to accept it.

Ok now for the Million Dollar question... there is a side "Screenshot" on the Module description which is also the main screenshot....

The devs just recently said in the patch notes... that it should appear if you have a screenshot with the Module Name in the Thumbnail in the... dungeons directory

Where exactly is that located on Steam?

nice

Got it now, there were multiple issues on this.

1. Originally it would not take jpg files when you attempted to upload screenshots FROM THE WORKSHOP PAGE.

2. SECONDLY... The instructions weren't very clear on getting the Thumbnails to show up in the module entry, and there was no way to do it from the Workshop interface... so no one knew how to actually do it.

So...

1. IF it will not take jpg files when you try to upload screenshots ON THE WORKSHOP PAGE, you just need to convert them in MS Paint program to a PNG file and REDUCE them in size until they're below the acceptable upload requirements.

2. BEFORE YOU PUBLISH the module from the Toolset and hit the Publish Button... you need to put your PNG or JPG into the FILE LOCATION where the Dungeon Module is ON YOUR COMPUTER... AND name it the exact same name as the File you're uploading.

3. Then when you publish it, it will post the Thumbnail.

4. AFTER doing that, then you can upload screenshots to your actual Workshop page from the Interface.

Looks like they changed the Size Requirements for the Thumbnails.

Now the pictures you have to upload from your local machine with the Name of the Module on them have to be below 1 meg in size.