First of all; there is no proof about Tony Stark and his religious tendencies presented to us in the Marvel Cinematic Universe.
However, as a scientist with a skeptical mind, it is more likely than usual that Tony Stark is not a religious man and in this instance I believe that a lack of proof is more likely to mean he is an atheist, rather than a theist. This is because he is a fictional character, and if an element of a character such as religion was important to them, it would be for a reason and be present in some form. The fact that it isn't means we can certainly say that religion isn't important to Tony Stark in the writer's eyes, and as such probably not important to the character either.
It's also worth mentioning that the lifestyle that Tony Stark leads both pre and post-Iron Man is hardly one that a religious man would live. He is a womanising, selfish, obnoxious and egotistical arms-dealer turned womanising, obnoxious and egotistical walking weapon. That hardly screams religious to me.
That being said, the very nature of the picture you refer to is wrong. Asgardians, at least in the Marvel Cinematic Universe, are categorically NOT gods.
It has been mentioned multiple times, from Thor to The Avengers/Avengers Assemble to Thor: The Dark World that Asgardians are merely aliens with increased longevity, which has resulted in their culture progressing much slower than their technology, creating a world in which their advanced science is indistinguishable from magic to normal humans.
Additionally, even if Asgardians WERE gods, neither Captain America, Iron Man or the Hulk would have met two of them, as Loki is in fact a Frost Giant, not an Asgardian. Which means that when Steve Rogers says;
These is only one god ma'am, and he doesn't dress like that.
He's closer to the mark than it may appear.
Note: I appear to have created something of a... kerfuffle in the comments below regrading my answer. In no way am I saying that intelligence and religion are mutually exclusive. However, this article shows a solid correlation between American scientists and a non-theism when compared to members of the American general public. As such, despite people's urge to find offence in what I have said, the likelihood of Tony Stark being an atheist is higher than that of the general population. This, combined with all the other points mentioned above, speak volumes (at least to me) about Tony Starks religious tendencies.