You may use any modelling software that exports 3D objects in a supported format for SH3D (like .dae).
For furniture I strongly recommend Google SketchUp.

In the dialog window that lets you choose a texture to apply you have a button: import. Use it.

<t>Right click inside the room and select modify rooms.<br/>
Then change the wall base to a tile texture that you like. If you want all the wall to be covered with tiles, select that option from the same window.For bases you can specify the height, meaning that a 7 cm height lets you create a plinth ...

<r>Hi, I'm a new Sweet Home user, although I've been using before modelling and rendering softwares.<br/>
This is a rendered scene that, I believe, looks ok, not professionally speaking, but as amateur.<br/>
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<IMG src="https://thumb.ibb.co/fZwTYb/baie_mansarda_var1.png"><s>[img]</s><URL url ...