The City of Palo Alto created cart corral signs, posters, signs, static window clings, reminder kit, etc. for its reusable bag campaign. The theme is the lonely bag that wants to be taken shopping. It would like to share the art with anyone (non-commercial) that wants to use it. Your graphic designer can just switch out their logo and contact info for yours.
Since running that campaign, the City has banned plastic bags.
There are three folders of materials available on request in both PDF and Adobe InDesign formats.
Store Collateral: shopping cart corral (available in 12x18, 12x24, and 24x24), checkstand signage, floor decal, Hframe, and 36x84 poster. Sample PDF
Reminder Kit:spec sheet, holder, decal
Links: related EPS and TIF files