I ummed and ahhd about posting this but it's fairly evocative/iconic in that we may have become a bit blasé about the fact that drivers ultimately risk their lives for our entertainment and this brings a touch of reality to all the 1 finger salutes.
MCLS I know what you mean. I took that screenshot from a video. We all know when it was taken. I think it tells you more than a thousand words. I don't want to be overinterpreting, but it seems that you can feel, that he fears something might/could/will happen.
I don't know if I saw that in the Senna movie or somewhere, but I remember Alain Prost saying that Senna approached him during the Imola 94 weekend asking him to come back, because he would rather have his old rival back than having to fight against the "cheating" Benetton team. That's pretty intense stuff considering their mutual history.
I know there is no connection between that Prost/Benetton stuff and this picture, but to me all those things (incl. the accidents of Rubens and Ratzenberger) all add up in that expression, which makes it very powerful and iconic to me. And it makes me sad.