Thank you for contacting Telerik Support.
The Thumbnail strip already offers this functionality. Go to Image Gallery Settings
and check the show only limited number of items
box. Then just pick the number of thumbnails you want exposed.
Don't hesitate to contact us if you have any further questions.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items