As pretty as a picture
Definition 1 of 1
Pro Tip 1/3Positive Connotation
The phrase carries a positive emotional charge and suggests purity or innocence. 
The children's choir sounded as pretty as a picture.
Pro Tip 2/3Visual Imagery
It evokes a visual scene that's delightful to look at, sharing traits with well-composed artworks. 
The flower garden was as pretty as a picture after the rain.
Pro Tip 3/3Complimentary
Primarily used to compliment someone's appearance, often in a quaint or charming way. 
Grandma said I was as pretty as a picture on my birthday.