To show a name on the image thumbnails (instead of the auto-genertated number) you must take the following steps:
Click on the profile of the tour
Click on the pencil next to each image
Add the name if the image in the box & save
You should rename your images BEFORE you create your tour. It will save you time in the long run. If you rename your images AFTER you built your tour, you need to go into the tour editor > settings and on the tab “scenes” click “save” 1 time and re-publish the tour to see the new name changes on your live tour.