This is the most unsatisfying answer to a question of extreme creative possibilities. I understand the idea, and yes, it has value, but technically we already have spaces in our written language. The joy in designing a new letter is stretching your imagination to endless heights, not re-inventing what already exists.

I like this idea of a negative letter, space. Much of design is essentially reinvention or reinterpretation, so I have to disagree with the above comment. Of course it's always interesting to see an entirely different and new creation, but it's often just as interesting (and satisfying) when someone's able to point out what's already there and give it a newly relevant identity. Language itself, through the ages, has been a product of modification after modification, and even today, language is reinventing itself, whether through new slang, shorthand forms of email/text communication, or redefining standards of proper style/usage in formal English.

Interesting note: There used to be a 27th letter at one point; it was the ampersand.