"Are people with a vivid imagination... crazy?": Doesn't it depend from person to person? With so many people and views on the world, even a person who could be classified as 'normal' could be determined crazy by a simple difference in opinion. What defines and separates people and their individual levels of sanity is just a matter of perspective. However, perspective that focuses on what can and can't be seen by more than one person bears an increased level of scrutiny by the other, this of course, is represented in imagination.
As an attribute itself, there aren't many who can deny that one's possession of an imagination is anything less than valuable; people with imagination can inspire, design, create, fabricate, theorize, etc. better on a whole than people without it, though in moderation. Certainly at low levels imagination is helpful in that it adds an edge to one's productivity and can help boost that person closer to their goals. However, as the level of the imagination and the creativity it inspires increases, it begins to distort and dissolve increasing portions of the world beyond one's mind, ultimately lowering external production. It can even be said that high enough levels of imagination and creativity can be dangerous; often invoking delusions, nightmares, and a failing grasp on reality, provided that the person in possession of this higher level is unable to control or differentiate figment from reality.
Thus - back to the question - 'are (these people) crazy?' The answer is: Not necessarily. Given the definition of either crazy: 1. Affected with madness; insane. 2. Departing from proportion or moderation. Or insanity: 1. Persistent mental disorder or derangement. 2. Unsoundness of the mind. 3. Extreme foolishness; folly. To lump all people together into one definition when people are innately different is wrong. The main question in perspective is whether that person's level of control is strong enough that they bear little difference form their peers on the outside, or whether their control is so lax that their internal worlds dominate not only their thoughts, but their lives in view as well.
What it all comes down to is two factors: on one hand there is a vivid imagination, on the other is the level of control the wielder dictates. Then there are two people, the normal and the crazy (for sake of argument there isn't an in-between state). Leaving out the various mental illnesses, disabilities, or other causes of insanity and focusing solely on vivid imaginations, this is scenario. Of these two types of people half of the normal groups are actually those with a highly vivid imagination, but they are virtually invisible. Why?
Let's toss away the intangible and focus on something we can visualize, possibly the imagination as a sword. Now, this sword of creativity and imagination from one person to the next is nothing alike. No imagination equals no sword, and among our groups of people there are many variations ranging from pocketknives, machetes, rapiers, katanas, and broadswords. While smaller may be less imagination, it could also represent a greater level of control and that the blade at hand may be extraordinarily dense and unbreakable. On the larger side there are swords so large they can't be moved or swords so dangerously shaped the cut the hands of their user. These larger and more dangerous swords represent the people we call vividly crazy. With their swords, these crazy people will either live and find a way to reshape their dangerous weapon (more control, less crazy), or they will be hurt, wounded, or even eventually killed by their lack of control (death signifying their loss of sanity to their imaginative world). However, with the proper outlets nothing as to remain in either sense and even normal people can acquire their own swords.
So in the end, is a person with a vivid imagination crazy or not? The truth that their thoughts are clearly different from others and thus places them in that category doesn't necessarily mean they have to be seen as crazy. In the end, crazy or normal thinking has no bearing on your outside image if you have the necessary control to see it through. No matter who you are; whether you are seen as crazy or normal, that depends on you.