I came across this image and it looks to me like fan art. My question is if it is just something someone did because they liked the concept, or if it is based on an anime or manga, because if it is I'd really like to check that out.
The girl in the image I at first thought might be a Uhlan, but the helmet, jacket and cartridge belt are for an Imperial German infantryman, although the lance, saber and horse are correct. As I looked at the image more closely I noticed the belt buckle was not standard: it has the badge of the Prince of Wales on it. Interestingly enough that badge bears a motto which is in German: "Ich Dien" or "I Serve", which is a motto any samurai would agree with.
So you see why I am interested to find out, even by the slimmest chance, if this is related to any anime or manga.