CI configuration to specify docker image per job

It would be very useful if we could specify the docker image at the job level as an optional override of the project level image. This would let us use appropriate tools from the Docker image depending on the job at hand.

E.g.

image: maven:3-jdk-7

build-job: 
  script:
    - mvn clean install

deploy-job:
  image: ansible:ansible
  script:
    - ansible-playbook application.yml

The build-job would execute using the default maven:3-jdk-7 docker image, but the deploy-job would execute using the job defined ansible:ansible docker image.