Take a look in the corresponding folder of your webspace (<joomlaRoot>/images/joomgallery/thumbnails/<yourCategory>/<filename.jpg>) is the thumbnail image available on the server?
Hi, yes, I can see the thumbnail in this folder.
Did you get any error messages during upload? Have you enabled the Debugging mode when uploading?
I've uploaded the pictures before I uploaded the module as I already have Joomlimages portfolio page. I just decided to show the images on the front page though the module as well. On portfolio page they show up fine.
If it is easier, I send the link to the website: http://dbnew.fishkadesign.com/en/