You may be right about that Sinatra picture. I can't tell.

http://www.thechipboard.com/index.cgi/page/1/md/read/id/1437535/sbj/50-hot-stamp-sands-las-vegas-sinatra-dealin/

The movie "Meet Me In Las Vegas" (1956) had some scenes filmed at the Sands:

As you said, Sinatra also did a brief appearance in the film: