The theory of applied photography distinguishes the category of so-called Universal photos, which are suitable for multiple documents due to having the same requirements for e.g. poses, but above all the size of the photo. Because the vast majority of photographers in Finland sell pictures for documents in sets of 4 or 8 identical shots, it's worth knowing where these can be used, because usually one picture is all you need.
The most common dimensions used for photos are 3.5 x 4.5 cm photos (passport photos size) in Finland. Those photographs are usually suitable for such documents as ID cards, passports, driving licenses, student IDs, transport cards etc...