Thumbnail on play

Have a look at:

http://blog.lilybiri.com/poster-image-autoplay

You can add a poster image, under Preferences, Project, Start&End

You'll no doubt get some other responses to this but I wanted to offer you another way of thinking about this if you're interested. It involves a little JavaScript modification up front for some nice rewards in my opinion.

Here is a link to a thread on this topic if you wish to pursue that thought further.

https://community.adobe.com/t5/captivate-discussions/so-you-re-looking-to-get-rid-of-that-white-screen-with-play-button-eh/m-p/10780736#M275893