Someone who believes that nothing made everything.
A scientific impossibility!
When I saw it from far away, at first I could only see that it said "atheist". The rest was just too small. As I got closer I could read the next two lines, but because if a large truck between us, I didn't catch the URL. I was actually quite thrilled to see it there, because the word alone is something that I would like more people to be aware of. I don't think you can change very many people much by such statements alone, but I think it can get some to look into the matter. And if they take more than a cursory glance at our present understanding of nature, they will most likely not come away with the idea that atheists believe that nothing made everything, nor that something coming from nothing is an impossibility.
First off, ignoring all fears of generalization, atheists disbelieve that a supernatural being created the universe. Specifically, we don't believe in gods such as Yahweh, Allah, Krishna, Odin, Zeus, Elvis, Usen, and Xenu, nor anything else with god-like powers that you may think of (yes, I am aware that such powers need to be precisely defined to make rigorous sense, but I think you'll agree that the meaning is clear nonetheless).
The disbelief of an atheist may entail a belief that the universe originated from nothing (though it may also not) depending on your cosmological model of preference, but it emphatically does not mean that everything comes from nothing. (I will not here consider the completely asinine idea that nothing made anything.) Once something exists, there is no reason to argue that things that originate after that comes from nothing. If by everything you mean "the Universe", then perhaps, but people might - with a picture of Darwin right there - take it to imply that atheist believe that other things comes from nothing. Which we don't. All scientific theories of origins but the theory of the Big Bang posits that things come from something.
As for the Universe coming from nothing, it actually isn't the scientific impossibility that is so often proclaimed. Quantum fluctuations is a case in point. In the words of Nobel Laureate physicist Frank Wilczek: "Nothing is unstable." For a great review of one current understanding of the issue, see this essay by Victor Stenger: Why Is There Something Rather Than Nothing?
Incidentally, Darwin (in the picture) was not a declared atheist, and to my knowledge he never said anything implying that nothing made everything, which sounds more like a statement from the realm of cosmology. But, he is of course the big bad bogeyman of the creationists, and a picture of Einstein just doesn't carry the same negative connotation to them, even though it was his equations that lead to the theory of the Big Bang.