Here are attributes and their values, as described in CUPS-IPP-1.1 document.
The blackplot attribute specifies whether HP-GL/2 plot files should be rendered entirely in black ink (blackplot=true) or using the colors and shades specified in the file (blackplot=false). The default value is false.
The brightness attribute specifies the overall brightness of the
printed output in percent. A brightness of 100 is normal, while 200 is
twice as bright and 50 is half as bright. The default value is 100.
Brightness is applied to the Cyan, Magenta, Yellow, and Black values
using the function "f(x) = brightness / 100 * x".
The columns attribute specifies the number of columns to generate when printing text files. The default value is 1.
The cpi attribute specifies the number of characters per inch when printing text files. Only the values 10, 12, and 17 are currently supported. The default value is 10.
The fitplot attribute specifies whether to scale HP-GL/2 plot files to fit on the selected media (fitplot=true) or use the physical scale specified in the plot file (fitplot=false). The default value is false.
The gamma attribute specifies the luminance correction for the
output. A value of 1000 specifies no correction, while values of 2000
and 500 will generate lighter and darker output, respectively. The
default value is 1000.
Gamma is applied to the Red, Green, and Blue values (or luminance for
grayscale output) using the function "f(x) = x^(1000/gamma)".
The hue attribute specifies a color hue rotation when printing image files. The default value is 0.
The job-billing attribute provides a text value to associate with a job for billing purposes.
The job-hold-until attribute specifies a hold time. In addition to the standard IPP/1.1 keyword names, CUPS supports name values of the form "HH:MM" and "HH:MM:SS" that specify a hold time. The hold time is in Greenwich Mean Time (GMT) and not in the local time zone. If the specified time is less than the current time, the job is held until the next day.
If only one value is supplied, the banner file is printed before the job. If two values are supplied, the first value is used as the starting banner file and the second as the ending banner file.
The lpi attribute specifies the number of lines per inch when printing text files. Only the values 6 and 8 are currently supported. The default value is 6.
Contrary to standard way, CUPS accepts more than 1 media attribute, eg. "GlossyFilm" + "A4". See standard attributes page for common media syntax.
The mirror attribute specifies whether pages are mirrored on their X axis, which is useful for printing transfer images on special media. The default value is false.
The natural-scaling attribute specifies the scaling of image files with respect to the natural image size. A value of 100 specifies that the image file should exactly the natural size, while 50 is half the natural size and 200 is twice the natural size. The default value is 100.
The ppi option can be used to override the natural resolution of the image, which controls the natural size.
The number-up-layout attribute specifies the order each input page is placed on each output page.
The page-border attribute specifies whether a border is draw around each page.
The page-bottom attribute specifies the bottom margin in points (72 points equals 1 inch). The default value is the device physical margin.
The page-label attribute provides a text value to place in the header and footer on each page. If a classification level is set on the server, then this classification is printed before the page label.
The page-left attribute specifies the left margin in points (72 points equals 1 inch). The default value is the device physical margin.
The page-right attribute specifies the right margin in points (72 points equals 1 inch). The default value is the device physical margin.
The page-set attribute specifies which pages to print in a file. The default value is "all".
The page-top attribute specifies the top margin in points (72 points equals 1 inch). The default value is the device physical margin.
The penwidth attribute specifies the default pen width in micrometers when printing HP-GL/2 plot files. The default value is 1000 (1 millimeter).
The ppi attribute specifies the resolution of an image file in pixels per inch. The default value is the resolution included with the file or 128 if no resolution information is available.
The prettyprint attribute specifies whether text files should be printed with a shaded header and keyword highlighting (prettyprint=true) or without additional formatting (prettyprint=false). The default value is false.
The saturation attribute specifies the color saturation when printing image files. A saturation of 100 is normal, while values of 50 and 200 will be half and twice as colorful, respectively. The default value is 100.
The scaling attribute specifies the scaling of image files with
respect to the selected media. A value of 100 specifies that the image
file should fit 100% of the page, or as much as possible given the
image dimensions. The default value is unspecified.
The scaling attribute overrides the ppi attribute if specified.
The wrap attribute specifies whether long lines should be wrapped (wrap=true) or not (wrap=false) when printing text files. The default value is true.