If working in Numbers, the solution to doubling the height of the final repeat for mazes or mosaics may be achieved by simply doubling the height of each cell prior to screen grabbing the table and processing the resulting image in Gimp. Here the cells for a single repeat in the table on the left are copied, pasted, and altered from 20X20 pixels to 20X40
Working in 1800 magnification, using rectangle select, every other pair of rows is chosen and then color inverted. B: the process continues for the height of the repeat. Until each new pair of rows is selected fully, the last color inverted pair is bordered in a dotted outline C, useful in tracking the last worked location. As the subsequent pair of rows is selected fully, the dotted border will disappear. 
The processed repeat 
Its tiled visual check 
Proof of concept: the bottom half is knit using the slip stitch setting, the top half in the tuck setting. The added texture on the tuck stitch purl side makes the fabric a more interesting, reversible one, and wider than its companion. 
For a different way of working with two-color initial images using only Gimp, see tips in Gimp update for Mac2.The process used on the beginning repeat, redrawn in 2 colors and then, in turn, elongated X2 or drawn double long to start with, tiled to check alignment. 
There are 2 options for altering colors in 2-row segments to achieve the separation, the first is color invert, the second is value invert, found in the colors menu. Both require color filling in of cells so as to obtain the final BW image, the value invert option, in this case, would require only filling in the green to white, but in managing larger images I believe having the additional colors make the process easier to track accurately. 
The color invert option will substitute a third color and white on every other pair of rows. Flood fill the original color 2 on rows containing black pixels with white, then fill color 3 pixels with black on rows containing white pixels: 
The mazes that are often seen in game-playing, puzzles, historical sources ie in Chinese design references, may not work out for knitting with this method, the result can be quite muddied. I recently found a new to me online maze generator http://www.ludiculus.com/maker/mazes.html. Changing the pixel width by default also doubles the image in height, making smaller designs for knitting problematic 
This was a quickly drawn maze using it, shown with its cropped repeat on the right, then tiled. 
Numbers processing to ready the repeat for final gimp editing: 
The repeat when tiled predicts muddied results 
which are noticeable in the knit swatch. Because of the side-by-side areas with multiple white cells, the slip setting is used, not tuck. The single slipped lengthened stitches do not produce an easily recognized secondary design on the knit side 
Getting back to clearer pattern results: when using electronics, it is possible to create far wider and taller repeats for download. The technique to achieve them uses the same process. A new working repeat: 
its tiled appearance 
My starting table in numbers with hidden rows, beginning to isolate a smaller repeat 
the isolated repeat, double-length 
the color separation in progress
When knit, that white cell pair of rows break up the overall shapes and shifts the pattern in the top and bottom half 
When I tiled my next draft, I decided I preferred a cleaner join at the center
The final adjusted repeat 
knit using the tuck stitch setting in both directions, KCI, first row left to right, leading with the dark color 
and here with the lighter color 
In progress, on the km 
the relaxed, 3D-ish view on the reverse 
why projects can take longer than planned 
The finished, relaxed scarf with pressed edges only, retaining the conical striped forms
The repeat knit double length, changing colors every 2 rows, becomes something quite different, with a sharp curl to the purl side 