I apologize for the delay in replying.
Yes, images in demo versions are only for demonstration, they aren't included in the package for sale. But except images all is the same as on demo version.
To insert images, please use this documentation ordasoft.com/template_documentation/joomla-gymhall/
Template Sections -> Homepage
If you have other questions, don't hesitate to write them here, we'll be glad to answer them.