People are very opinionated on exclamation points. Some don't mind them, while others are harassed by them, similar to you. However, iconography is all about familiarity. The idea is to convey a idea with a simple image, so part of that means relying on convention and what people are used to. In this case, you're basically talking about "caution" and the near universal symbol for that is a yellow triangle with an exclamation mark inside. That means you need to play off that at least a little. Yellow conveys the idea pretty well on its own, but only on its own. Combined with non-standard symbology, you're likely to confuse. You can probably get away with a yellow triangle, sans-exclamation point, since that conveys most of the standard iconography people are used to.
Other than that, I would say embrace the exclamation point. While it may convey rocks about to fall on your head to you, it doesn't to everyone, and in situations where there is real danger, the symbolism is red and skull-and-crossbones. Exclamation points are not actually used here. Even when the word, "DANGER" is presented in signs, it is not usually followed by an exclamation point. In truth, this reveals a subtlety of the language as an exclamation point only implies emphasis, not yelling. For yelling or excited utterances, all-caps is almost universally employed, instead.