Imagination - the faculty of imagining, or of forming mental images or concepts of what is not actually present to the senses.

A lot of people think that imagination allows us to imagine anything that we want, however, the truth is that we're either recalling something we've already experienced or combining several experiences into one.

Example:
Imagine a house. You'll probably recognise this house, it may be your own or it may be one you've seen elsewhere. Now try to imagine a house you've never seen before. Although this house seems to be new, it is likely to be made from your memories of other houses you've seen, it may be large like a mansion or small like a bungalow, but either of these will have been recalled from memory.
Ok, you say, i'll imagine a pink mansion with yellow spots and a giant umbrella out the top; I've never seen that before. However, this is simply combining several images/concepts into one image.

As far as I can tell, everything we try to imagine is simply a different way of recalling our experiences. Many people also derive inspiration from our dreams, but arguably, our dreams are simply re-organising experiences in a way we've never thought of ordering them before, rather than imagining completely new concepts.

Now try and imagine something that no-one has experienced, try to imagine infinity. If you imagined an infinite length of string, you'd find it hard to grasp the concept of a true infinite string, as you stop imagining it when it goes outside your imaginary vision. You can take a mental step back to see more of the string, but you never actually reach infinity.

The point of this rant is as follows:
Is it possible to imagine something completely new, something which is not derived from pre-known experiences or concepts?