When it comes to interior decoration you can't get more trad and timeless than distemper. Possibly the oldest paint in existence, it consists of hide glue (made from boiling animal hides: same as gelatin, edible), chalks, possibly pigments of some kind. Water soluble, non-toxic. 
On hard surfaces, Neanderthals used a variant of distemper (but with a tar based binder rather than hide glue) for their cave paintings. Ancient Egyptians used it in their tombs (this one ca. 1,500 B.C.) and the Ancient Romans for wall paintings in Pompeii (early 1st c. A.D.).
On softer surfaces it was used by Egypto-Romans for funeral surfaces on wrappings or wooden boards, often as a base layer to stiffen the surface material before using other organic paints such as tempera. Both these probably ca. 160-180 A.D.
It was used on cloth in Tibet (here ca. 1200-1250 A.D.) and on linen canvas in Europe (here The Annunciation by Dieric Bouts, Louvain, Belgium, ca. 1450-1455).
In Europe and its colonies it was the most common interior paint until the late 19th c., but used extensively especially for ceilings until 1950. Here Sweden, ca. 1853, an Australian restored room ca. 1910, a very recent Danish palace restoration.
Distemper is thick, cheap, safe, breathes perfectly (no mold) and washes off cleanly and easily with water: applied last week or 6,000 B.C. The dried un-prepared animal hide glue lasts indefinitely. In Egypt pots of it has been found in 4,000 year old workshops: ready to boil up.
If you want a clean safe interior paint that will never look out of place or out of fashion, please read up on distemper. Especially if you have children. It isn't a tough paint but if something goes wrong just make up a new batch. From dust to dust...
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