Prints The prints are made up in two series. Some are labeled "Print" and some "Poster" for reasons best known to Zazzle. I have ordered samples of the prints and found them satisfactory.
11x14 This group largely contains fractal art. The size was chosen because it is a standard frame size. Many of the pictures have a 1 inch border, some do not. Source files 400 pixels/inch.
Large This group contains many of the algorithmic landscape pictures. Most of them are in 20x28 or 20x30 inch sizes, with a few 24x24. Source files 300 pixels/inch.
Paper Zazzle offers 5 paper types. The "card stock" is not recommended in any case. "Value poster matte" is a good general purpose paper. "Value semigloss" is much like semigloss photo paper and has somewhat improved resolution. "Archival heavyweight" is recommended for the large pictures and offers a gloss-free high-resolution image. The canvas choice seems poorly suited to this Johnre.
The image sizes are fixed because John does not think that these images with their wide range of feature sizes look good in small sizes. Much of what is interesting is lost. Custom pictures can be arranged with John by contacting him by EMAIL.
Mugs I have a number of them and have found the color and resolution to be good and the images to be dishwasher safe.
Calendar The reproduction of the images is quite good. The calendars also include John's somewhat whimsical choices of two quotations for every month and a description of the month's image.