Is it no longer possible to upload a custom thumbnail for your YouTube videos using the new YouTube info and settings panel in the video manager? I read articles saying click the Upload thumbnail button, but I see no such button (see screenshot):
Upload custom YouTube thumbnail?
youtube
Regular user accounts are unable to upload custom thumbnails for their videos, however, Youtube partners are able to upload their own custom thumbnails.However, doing a little searching apparently there's a grey-hat way to do this for non-partner, but there's a pretty big risk in using this method since Youtube could ban your account: Custom Thumbnail for Non-Partners