Presenting your brand logo with foliage is a unique environmental statement. Not only can it reflect a brands sustainability policy, but it can also help justify the expense of a living wall. You can see some examples of this in Billboards & Branding.
Living Wall Benefit
As in this example of Marks & Spencer, using a sign in front of the living wall allows for accurate branding.
Using illuminated signs can draw more attention to both the living wall and the brand message.
As in this example from a residential situation, wording can be achieved in the planting.