Simple gulp task to cache bust image urls in css.

background.png

gulpfile.js

var gulp = require('gulp');
var cssImageHash = require('gulp-css-image-hash');

gulp.task('images', function() {
  return gulp.src('./background.png')
    .pipe(gulp.dest('./build/'));
});

gulp.task('css', ['images'], function() {
  return gulp.src('./style.css')
    .pipe(cssImageHash('build'))
    .pipe(gulp.dest('./build/'));
});

gulp.task('default', ['css']);

package.json

{
  "name": "gulp-demo",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "dependencies": {
    "gulp": "^3.9.0",
    "gulp-css-image-hash": "github:d3r/gulp-css-image-hash#44a0c8108d"
  },
  "devDependencies": {},
  "author": "",
  "license": "MIT"
}

style.css

body {
    background: url('/background.png');
}

The result is build/style.css containining this:

body {
    background: url(/background.png?h=85ae028f5ee9f56909efd3977141ee03);
}