its not about how long its about whether you've made your point in a metaphorical way or not. I'm writing one now. its a pain lol thanksssummm who r u I posted this question xD but thanks for...
vi·gnette n. 1. A decorative design placed at the beginning or end of a book or chapter of a book or along the border of a page. 2. An unbordered picture, often a portrait, that shades off into the...
a short, usually descriptive literary sketch
Depends what context you use it in.
http://www.google.com.au/search?hl=en&rlz=1T4GGLR_enAU293AU293&q=define%3A+vignette&meta=