Not sure if this will help, but I use a program called Post Razor to print large pictures. I like the fact that it saves the new size as a PDF, and I can print what ever pages I need at the time. I tested out printing a 4000x4000px map, and the detail was very good. I have a Epson NX330 printer, and I am using 2nd Hand ink cartridges from Amazon, so the ink is not the best. But the print was very good, and I was surprised at the quality.
http://posterazor.sourceforge.net/

About:

The PosteRazor cuts a raster image into pieces which can afterwards be printed out and assembled to a poster. As input, the PosteRazor takes a raster image. The resulting poster is saved as a multipage PDF document. An easy to use, wizard like user interface guides through 5 steps. PosteRazor is available as a Windows, an OSX and a Linux version. It is an open source, GNU licensed project which is hosted on SourceForge.net.


Features:

Input image formats
All image formats that FreeImage can read should be usable as input for the PosteRazor:
BMP, DDS, Dr. Halo, GIF, ICO, IFF, JBIG, JPEG/JIF, KOALA, LBM, Kodak PhotoCD, PCX, PBM, PGM, PNG, PPM, PhotoShop PSD, Sun RAS, TARGA, TIFF, WBMP, XBM, XPM

Image types
PosteRazor can handle the following image color types:
Monochrome, Grayscale, 4 Bit palette, 8 Bit palette, 24 Bit RGB, 48 Bit RGB (only via TIFF and PNG), 32 Bit CMYK (only via TIFF)
32 Bit RGBA images can be loaded, but are transformed to 24 Bit RGB by "merging" them with a white background.

Dimension Units
Because people around the world invented so many different dimension units, PosteRazor supports quite a few:
m, mm, cm, inch, ft, pt(72th inch)

Printer page layout
The page size and orientation of the printer where the poster will be printed can be set manually or selected one from the following list of predefined formats:
DIN A4, DIN A3, Legal, Letter, Tabloid
The size limit for one page is 5 meters (16.4 feet), which is the maximum that PDF allows.

Poster size
The size of the final poster can be set one of these three ways:

Absolute image size
You want to have a specific size of your poster.
Size in Pages
You want to use whole paper sheets and specify how many of them of them you want to use.
Image Size in percent
Your input image has a certain size which is defined by the number of pixels and dpi (dots per Inch) and your want to scale the image by a certain factor.

The final size of the poster is theoretically unlimited. Let's say it this way: it is less limited that the ink of your printer

It is possible to select the alignment of the image on the total paper. This is useful if you want to keep the unused paper.

Image tile overlapping
For a bigger tolerance when cutting spare paper borders and for easier pasting, an overlapping width and height of an image tile over the next can be set.

PDF output
The PDF output is implemented with the maximum image quality and a good compression in mind. A source image is embedded once in the PDF document and referenced from every tile page. Image color types remain unchanged. As compression method, the PDF "FlateDecode filter" (zip) is used. If a Jpeg image is used as input it gets directly embedded into the document without recompression. The PDF version is 1.4, so any Acrobat Reader version 4 and higher should be able to read the resulting document.

Missing features: Cut lines/aids; Support of Jpeg-CMYK images; Support of 16 Bit Grayscale images; Embedding an ICC profile into the PDF if there is one embedded in the input image