I'd actually focus Gav's point a bit more to put it like this:
Our thoughts are limited by that which we can symbolically represent. The most widely used symbolic representation is spoken/written language. Others can used gestures, pictures, symbols, etc. to represent thoughts.
Take for instance the words "disinterested" and "apathetic." Similar meanings, but subtly different in how we use and perceive them. There's a fair amount of literature to suggest that, for a particular example like this, we will have a hard time feeling "apathetic" as opposed to "disinterested" (the emotions associated with those words) until we understand its meaning. The ability to internally represent the emotion via a spoken word gives us access to that emotion. The ability to feel apathetic is learned through symbolic representation, rather than vice-versa, where we assign labels to emotions that bubble up instinctively. The biological responses may be there before a label, but we don't experience something until we have a way to internally represent it.
The common cry against this is something like small babies, who undoubtedly feel "happy" and "sad" despite not knowings such words. True, but we can't limit internal representation to established languages. Babies have internal symbols that help them mimic happiness (their mental images of food, parents, etc.), though the emotions are clearly not as nuanced as those that language allows for. But whereas we may eventually generalize "happy" into a single emotion due to language, they may even have similar but not identical feelings associated with "food-happy" or "dad-happy" etc. etc. due to differing representations of such events.
Moral of the story: want a bigger imagination? Get a bigger vocabulary, and read as much as possible. It falls on deaf ears in the classroom, but I believe it to be very true.
As for WD's question, our imaginations are already gods. Give our imaginations control over reality and there'd be no limit to its ends. It's just our bodies that have yet to catch up, as well as the physical world around us limiting those imaginations.