If the background changes angle / view smoothly as you move, it must be modelled with a 3D frame. The textures mapped over the objects could be drawn or taken from photographs.
A static background that only changes from scene to scene could be a plain image, or captured from a rendered model.
The original id software Doom / Quake games are good for examples of how 3D games work, they have open-sourced all the older game engines and there are vast numbers of add-ons and higher resolution character skins & textures etc. to improve the appearance.
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Just searched the game name on youtube & there is a full walkthough - they are just static drawn images, sometimes layered so the character can move behind parts of objects or scenery.