Import "flat" floor features

Occasionally, I want to add custom "flat" features to a floor. Examples for this would be, for example, carpets made for a rich merchant so that he has similar carpets in all rooms, or a Nobles' coat of arms as an inlay in his wooden floors, or – most importantly – teleport circles for a "West Marshes" – style campaign. So far, I have not found any way of adding these. As they are flat assets, they would not interfere with 3D rendering, but would have to be placed underneath 3D assets such as tables, chairs and similar.

It would be great if you could enable something like this.