Is it possible to sell one pixel at a time, of if it can be configured to do that.

No, pixels have to be sold in blocks. Selling a pixel 1 at a time would be very inefficient. If you make a pixel for $1, then it could be that the transaction costs would amount to %30 or more. Also, it would not be attractive for advertisers, because you cannot put an image on 1 pixel. A pixel is no bigger than the dot at the end of this sentence.