Well, if you only want to “look at” one layer, as layer state changes get recorded by the undo stack, you can use OneLayerOn and then Undo when you’re done looking to get back to where you were.
Otherwise, you can use the LayerStateManager - which can be set up as a docked panel in V5 - to set up and save one or more layer states which you can then freely switch between. Unfortunately, if you add layers to the document after that, the layer state manager will not know about them.
To get around this you could:
First, set up a layer state where the one desired layer is on and nothing else. In the layer state manager, give it a name like “SeePlan”. Then, create a button in your Rhino workspace and on the left mouse side, macro something like:
-_LayerStateManager _Save "MostRecent" _Restore "SeePlan" _Enter
That will save your current layer state (no matter what it is) and then turn off all the layers except the one you left on when you created "“SeePlan”
On the right mouse of the same button, you can then put:
-_LayerStateManager _Restore "MostRecent" _Enter
-which will bring you back to where you were. The above will work even without the layer state manager being visible or docked as a panel.
Lastly, a perhaps simpler non-layer changing workaround for your particular need:
Make a copy of the picture frame image that you are using for your plan and put it on a another layer called, say “SeePlan”. Then move the copy in Z world above all other objects in the file. Lock the layer “SeePlan” for good measure. When you turn on that layer, your plan will appear above everything else; thus it’s all you will see. When you turn it off again, you will see everything else.