Arguably, cave paintings count as "home decoration", although not at all with the same meaning as, say, a Norman Rockwell magazine cover pinned above the kitchen table. We don't see much evidence of commoners' home decor until the Early Modern period, when consumerism ramped up with increasing availability of textiles thanks to innovation in mechanical production. A middle-class family could afford a carpet, wallpaper, perhaps a silver tea service or a few exceptional candelabras. Mass production of "kitsch" items started slowly in the 1700s; we have commemorative spoons and tea pots painted with Benjamin Franklin's face, for example.

As far as the Middle Ages go, you might actually look at "floral arrangements". Although bland in comparison to something like silk throws or oil paintings, flowers straddled the border between useful and sentimental; Medieval smells were formidable, with everything from open sewage channels to rotting animals corpses in the streets. Flowers and herbs, sometimes intricately woven together, would have a jolly presence in any home with access to a garden or a meadow.