How do I get thumbnails for videos?

[lindastacy]

I'm working on a new website (using WordPress) that will include videos embedded from YouTube, Google Video, etc, and I'm going to need thumbnail images. Is it fair use for me to make and host my own thumbnails from the videos? Or can I retrieve the [s]videos[/s] thumbnails and from the sites where the videos are hosted?

Thanks in advance.

Also if you have a recommendation for a good WP theme for videos I'm still looking.