I haven't yet printed my sideart but I can answer this question for you:
What does having the art vectorized do for you? Does that allow it to be printed on large format printers/plotters easier?
There are (in general) two ways of creating computer graphics: bitmap and vector.
A bitmap is a grid of picture elements (pixels) each with a different colour.
A vector is a mathematical definition of the graphic (for example a line is defined as the shotest connection between two points).
To enlarge a bitmap, the grid is just made bigger, the individual 'squares' of the grid are just bigger boxes which makes the image look blocky (some algorithms try to smooth things out a little but the end result isn't a clear image like the original).
To enlage a vector, some math would do the job and the image would still be crystal clear.
Both formats have advantages and disadvantages. A bitmap is suited for photographs or images with complex shapes.
A vector is sharp can can be rendered in all sizes and still look great hence it is perfect for on a high resolution printer.
I you want to use a bitmap for sideart of CP art, make sure the source material is high resolution (at least 72 dots per inch, preferrable 300 dots per inch or better).