All over the city — especially downtown — our buildings have advertising signs (AKA ghost signs). These old signs are fading and suffer when the brick walls get much needed repointing. Why not create one large mural that represents all (or many) of the endangered original signs? Each of the original signs could be reduced in size and placed within a patchwork of other signs to fill a large rectangular building wall?
On the ground, perhaps on a sidewalk with a good viewing angle, could be an interpretive sign which shows the signs in outline, names them, and explains where they are (or where) located. If there is room, a few details of the company or product can be provided.