Another tip to give your render a bit polaroid-like mood. The steps are:
1. Press Ctrl+M to launch the curves panel.
2. Click the drop-down menu where it says "RGB" and change it to "Blue"
3. Add a node in the center of the curve, and a second node in the middle of the lower half of the curve.
4. Move the second node up, so the curve takes the shape shown in the screenshot.