YouTube is making it easier for creators to customize video thumbnail images with these updates:

• YouTube Partner Program Creators can upload custom thumbnails for Shorts - and this will expand to more creators
• Choose from 3 suggested thumbnails for Shorts on desktop (if you're in the YouTube app on mobile you can pick any frame from the video)
• Chat in Ask Studio and it will create/adjust a thumbnail for you - the thumbnails it makes will be tailored to your video's themes & style