The Virgo symbol (also called Virgo glyph) is a shorthand representation of the Virgo zodiac picture (see below). However, as with the picture itself, much is based both in interpretation and the preference of the writer, and can range from simple to extravagant.
Above are some examples of commonly used styles for the Virgo symbol. Each of these is equally valid - there is no 'correct' version as long as the general shape is maintained.
The word 'Zodiac' means circle of animals (though note a couple of signs such as Virgo aren't animals in the normal sense). These 'animals' were based originally on the pattern of the stars in their corresponding star constellation. Basically what the earliest astronomers and astrologers saw when they squinted at the night sky.
Due to this although Virgo will always be represented by a virgin, there isn't any one 'correct' design for that virgin, though traditionally always depicted as female. It's a cosmic game of join the dots, and some constellations even have alternative ways to form the animal from the dots (stars).
Any picture of the shape, head, concept or profile of a virgin can therefore be comfortably used here. Designs range from the space-age to the ancient, and are limited only by the imagination of the artist, as long as it gets the point across.
Below is a representation of Virgo the virgin (and the Virgo symbol, inset) from a medieval wood carving from the 16th century. While it's not suggested this is a great picture (hey, you try carving something into the side of a tree which will look sexy in 400 years time!) it does show how the basic concept of Virgo the virgin hasn't changed much over the centuries.
I have a separate article on Virgo tattoos.