PreFlight - Preflight is an Automated Web Testing tool. Allows everyone to automate Web UI tests.
Ui Thumbnail Generator - A simple way to generate thumbnail. For docs and demos.
Videogram - Auto create interactive thumbnails (GIF card) of video
FilePreviews - Thumbnails and metadata for almost any kind of file
Thumbnail Test - A/B Test Your Thumbnails & Titles Live On YouTube
Blog Cover - Cover image generator for your blog post