You can fit the map to the image layer by double clicking it's name in the Layers tab, or by right-clicking and selecting Go To. This allows you go elsewhere after mapping the layer and not have to worry about finding it again later.

You can alter the opacity of a mapped georeferenced image by right clicking the layer itself, or by right-clicking it's name in the Layers tab, and adjusting the slider control.

You can resize/replace the georeferenced image by right-clicking the layer itself, or by right-clicking it's name in the Layers tab, and clicking Edit Layer. This process is the same as when the image was placed the first time.

Remove the layer from the map by unchecking the checkbox, or by right-clicking either the layer itself or it's name in the Layers tab, and clicking Remove Layer.