If you are interested in sustainability and want a green option for your next house painting project, you might consider going beyond the usual eco paint products. Most of them are fine paints, and feature low or no VOC content, but they are still necessarily manufactured with some synthetic materials that take a toll on the environment, just in lower quantities than conventional paints.
There are, however, some paints on the market that are almost entirely made from organic and natural materials; these are best referred to as natural paints. They are made with naturally-occuring pigments, and plant and vegetable oils as solvents, among others.
One very interesting type is milk paint, which usually comes in powder form, and is mixed with water before use. In Toronto, this can be purchased from Homestead House Paint Company. Milk paint is a great option for most interior areas, including walls as well as cabinets and furniture. It gives a very nice finish that is nearly flat and quite smooth. You can finish it in a natural clear sealer for added durability and colour depth, which is great on furniture to give it a unique look. Milk paint also lends itself well to antiquing and faux-techniques.
I have seen other natural paints that use clay and earth; it is surprisingly effective to use these green paints, as they offer a lot of the benefits of the standard stuff, but with no harmful odours and minimal impact on the environment.
More information about the types of paint can be found in this thorough article.