Having to scroll through image gallery thumbnails is a pain, especially on desktop. Users need to click the small scroll arrows.
The two options are:
- Show all thumbnails. This is a problem only if your product has more images than fits under the image gallery, so typically more than 10-15 thumbnails.
- Truncate and have a clear + button which opens a panel with all thumbnails.
If you reveal all thumbnails, do it in an overlay panel when users click any thumbnail (and include a truncation link).