i is not the only imaginary number. It is but the first number in a yet unsubscribed numerical system. It is metaphorically equivalent to the place of the number 0.
The number sequencing (such as 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ) of the imaginary system consists of all of all prime roots of any whole prime negative number. Unlike our Arabic number system, which has ten digits, the imaginary number scale is infinitely unique and never repeats itself. It instead overlaps.
The imaginary number system is not linear. The numbers do not stand next to each other in a line, but ripple outwards from the negative prime in a quantum manner. As there are infinite number of whole prime roots of each prime negative number, the main question in developing this theory is how to determine an ordered sequence of usable numbers.
While the use for the imaginary number system has yet to be discovered, it may help to describe the imbalance of energy which causes there to be a difference in the amount of matter and antimatter in the universe. As such that no 'real' equation has been discovered that can describe anti-matter, it may be that a yet unexplored system of mathematics is key to understanding it.
Any other root of negative one is undefined.
The next number examined would be the square root of negative two. From there outward, expanding infinitely, would be all prime roots of negative two.
Then to negative three, and then five. Seven follows, and eleven and thirteen. Et cetera, Ad nausium.
The points interest in the imaginary number system would be the intersection of similar prime roots of separate negative numbers.
No other symbols for the imaginary numbers have been created for this system.