Sure, here are 10 useful features for distinguishing an alcove in a photo:

1. Recessed area: An alcove is typically a recessed area, which means it is set back into the wall or structure. This can be a key feature to look for in the photo.

2. Arch or curved shape: Alcoves often have an arch or curved shape at the top, which can help to differentiate them from other types of niches or recessed areas.

3. Depth: Alcoves are typically deeper than other types of niches or recessed areas, so looking for depth in the photo can be a useful feature to identify an alcove.

4. Lighting: Alcoves often have different lighting than the surrounding area, which can help to make them stand out in a photo.

5. Texture: The texture of the walls or structure around the alcove can also be a useful feature to look for, as alcoves often have a different texture than the surrounding area.

6. Decorative elements: Alcoves may have decorative elements such as moldings or shelves, which can help to distinguish them from other types of recessed areas.

7. Placement: The placement of the alcove in the photo can also be a useful feature to look for, as alcoves are often located in specific areas such as corners or above fireplaces.

8. Size: The size of the alcove can also be a distinguishing feature, as they are often larger than other types of niches or recessed areas.

9. Perspective: The perspective of the photo can also be a useful feature to look for, as the angle and viewpoint can help to highlight the alcove.

10. Functionality: Finally, the functionality of the alcove can also be a useful feature to look for, as alcoves are often designed for specific purposes such as housing artwork or providing storage space.