Two-dimensional surfaces and Image entities can be scaled just as easily as three-dimensional geometry. The scale tool's bounding box contains nine scaling grips when scaling a 2D face. These operate in a similar manner to the grips in a 3D bounding box, and also work with the Command (Microsoft Windows) or Option (Mac OS X) and Shift modifiers.
The bounding box is a 2D rectangle when scaling a single 2D surface that lies in the red-green plane. The bounding box will be a 3D volume if the surface to be scaled is out of plane with the current red-green plane. You can ensure a 2D scale by aligning the Drawing Axes to a surface prior to scaling.