You can upload custom thumbnails on Instagram instead of using the default thumbnails. When you upload a video on Instagram, you can go over to cover and chance the main cover or thumbnail on the video. But it forces you to choose one from the actual vide

So, Here are Three Ways You can Add a Cover Image to an Instagram Post. Read How to Post on Instagram from PC. How to Add Custom Thumbnail to Instagram Video 1. Use Cover Feature. After you select the video you want to upload on Instagram, tap “Next”

Upload your image and use the bottom panels to add text, transparent images, and more to your collage. Click the background size buttons to choose a 1:1 or 4:5 ratio for Instagram. Or, click "Custom Resize" to make your output exactly 1080x1080,