pretty as a picture

Very visually attractive or appealing; having a picturesque beauty. The girls Alex dates are always pretty as a picture, but don't have much going on between their ears. This part of the country looks as pretty as a picture in the summertime.

very pretty. (*Also: as ~.) Sweet little Mary is as pretty as a picture. Their new house is pretty as a picture.

Very attractive, as in She looked pretty as a picture in her new hat. The noun picture alone was used to describe beautiful objects from the early 1800s on; this locution, however, dates from about 1900.

Singularly attractive. The picture in question means a work of art, and the expression dates from Victorian times, when, one might speculate, paintings often were “prettier” than today. Mark Twain used a version of it: “He was pretty enough to frame.” (A Connecticut Yankee in King Arthur’s Court, 1889). Although Dialect Notes in 1909 noted that the term was often used of a piece of fruit, which presumably was good-looking enough to paint, it was and still is more often applied to human beings.