These are steps that can be taken when images are not rendering when used as Thumbnail images of Site Categories.
Please follow the below steps:1) In the File Cabinet, navigate to the Images folder (i.e. Documents > Files > Images) and locate image file record that is not displaying correctly on your web-store.
2) Click Edit on the image record
3) At the bottom, under Publishing tab, locate URL Component field and remove any value it currently contains (so it is empty)
4) Save image record
5) Clear browser cache (or use another browser) to verify that Image is now displaying correctly on your web-store. Due to caching, it may take some time for changes to be reflected.
Repeat these steps for all affected images.