Thumbnail being created INSIDE gallery

For some reason, my site is automatically creating a thumbnail from the first image, adding _thumb to the file name, and then showing that in the gallery. It looks horrible because it's in reality a tiny image being stretched.

Any idea what could be causing this? I have to periodically delete that image, but invariably, it always comes back. I don't know what actually causes it to be created.

Here's the site: www.longscabinet.com . That at Rok slideshow on the home page. The Hot Joomla gallery is here: longscabinet.com/santa-cruz-san-francisc...ose-custom-furniture

Hot Joomla Gallery can't change or rename any images. There's no code for something like that in this module. This is probably done but another extension on your site.