For changing textures of 3D-models I use a custom models and change their textures in Deep Exploration than import models into SH3D.
When I want to add some stripes or another saped objects to the walls, I take a cube or round and change their textures and dimensions (length, width, height) in SH3D and plase them next to the wall. It looks like in this picture:

KT Exclusive_Damasse 6 by pixie Xu, on Flickr

The base of the walls was made in decorative plaster texture, than decorative frames was added on the needed levels. Than I took cubes that comes with program by default and changed thair properties, placed them on needed level. For that cubes I took textures of a wallpaper an murals (the antic lion of Affresco).