I found by accident the website of the Centro de Estudios de Historia de Mexico Carso, owned by Carlos Slim, and it has a large colection of digitized documents and photographs. I'm still browsing through the website, but I have seen there are some collections about Nueva Galicia and the war of independence. The site is:

http://www.cehm.com.mx/Es/archivo_digital/Paginas/Consulta_de_archivos_…