Determining the scale of your wallpaper depends on the goal you have for the room. You might want to make the small room seem larger, or you might prefer a more intimate look. In general, larger-scale wallpaper makes the room seem larger, while a smaller scale makes the room seem smaller.
The color of the room and the wallpaper is vital in determining the scale of your wallpaper. If the color of the wallpaper matches the color of the room, you can use a smaller scale because the wallpaper will blend in with the surrounding walls. White or yellow backgrounds make the room look larger, so a combination of a light color and a small pattern balances out the proportion of the wallpaper. Wallpapers with reflective or metallic surfaces work similarly. If the wallpaper is a bold color or contrasts with the surrounding walls, a larger pattern is more appropriate.
The amount of area you plan to cover with your wallpaper also affects the scale of the wallpaper. A smaller, busier pattern can work if it is used on one wall. It can serve as a feature wall in the room. If the small, busy pattern is used on every wall, it can quickly overwhelm the space and make the room shrink in perception. A larger pattern works on multiple walls or on the largest wall of a small room.
Certain small-scale patterns actually make your room look larger. These patterns include wallpaper samples that have small components but work together in a cohesive manner so they look like a larger scale. Some examples include a crocodile pattern, geometric patterns, certain floral patterns and stripes. Graphic and mural patterns are better in a larger scale.
Some wallpapers feature a texture on them. The texture provides an additional element of contrast to your room. A small-scale wallpaper often makes the wallpaper seem textured even if it is not, so you can use a smaller scale to add this textural element to your room.