Thea Darkroom in SketchUp has lots of settings for the rendering engine, display settings, environment, etc. In case you would like to have more real estate for the rendered image you can double-click on the horizontal space where the Save Image, Start and Stop icons are to minimize it.
Thea for SketchUp can operate either in Interactive or Production Mode. Even if we have selected a high resolution from the Camera Tab (Thea Tool window) while rendering in Interactive Mode, the resolution adapts to the size of the Thea Darkroom window. The same thing happens when we the in SketchUp window option is active.