Posterizer is described as ''s free online rasterbator allows you to create posters larger than a standard page, using the tiled printing method. It will rasterize any image and output files that can be printed at home and reassemble to the original image'. There are more than 10 alternatives to Posterizer, not only websites but also apps for Windows, Mac, SaaS and Linux. The best alternative is Rasterbator, which is both free and Open Source. Other great sites and apps similar to Posterizer are Posteriza (Free), pdfposter (Free, Open Source), Lucidpress (Freemium) and Separation Studio (Paid).
The Rasterbator creates huge, rasterized images from any picture. Upload an image, print the resulting multi-page half-toned pdf file and assemble the pages into extremely cool looking poster up to 20 meters in size.
This requires the installation of Python and pyPDF. Out of the gate, the script does not provide for image overlap, however there is a patch that does fix this. The patch requires replacing 5-6 lines in 3 files and adding 2-3 new ones, its very easy.