To control the size of the image we can resize the image in design view, but this will not be good enough, since the size of the room core is not actual size from the building block and we need to set a max width/height. The way to do this is to get the size you would like to use by changing the size in designer mode. In order to free form both width and height you must make sure that "Preserve Aspect Ratio" under Image Tools → Format is not checked. You can now preview to validate that max size is correct, but as you can see the image will not preserve the correct ratio. Open properties and then copy the values from Image → Content width/height to Width/height in Positioning and change from non-uniform to uniform scaling:
