may I humbly suggest?
Blackjack-
I am eagerly anticipating your new book! I too had some thoughts about the position of the balls in the diagrams, but quickly realized that you were really asking about how the balls look. I spent 10 minutes here with adobe illustrator and with just a little work produced images that I like infinitely better for a few reasons:
*you must make sure that your graphics have appropriate resolution AND are anti-aliased
*I would suggest changing the font to something sans-serif - my example below uses arial, but there are many options that are very readable
*text must be anti-aliased!
*I really object to using two different font sizes for balls 1-9 and 10-15 - most noticeable inside the rack
*I vastly prefer empty white balls, mostly because white text on black background is tiring to the eyes (subconscious to most, but known to graphically inclined). This is made worse because your stripes balls have an even smaller font. Also because its straight pool and the numbers are only there to go with your text (stripes/solids don't matter).
Here is an example graphic paired next to one of your original graphics. Again this is 10 minutes of work, so with tweaking, could look even better. Note that its the same native resolution as your images, but presents much nicer.
We can take the discussion offline if you want to get more technical, I would be happy to help out in any way that I can. Although I am not a professional graphic artist, I did stay at a Holiday Inn express last night.
Jon