New artwork is usually better than trying to clean up poor artwork.
An image off Shutterstock could help with creating acceptable sign work, but I always explain to a client that a logo design cannot incorporate images from image-licensing services. “Royalty-free” makes no difference. All images on Shutterstock are protected by copyright.
Most end user agreements at image-licensing services, including Shutterstock’s, forbid the use of their photos or artwork as part of a logo design or branding scheme.
Of course, the lettering only can be claimed as a protected logo, a trademark, assuming it identifies goods or services. But an image from Shutterstock cannot normally be claimed, or protected, as a logo design, or as part of a logo design. Most image-licensing services have this policy. Hence, when you obtain an image from Shutterstock you are not actually buying the image, but just licensing it for limited uses. Using the image as part of a logo design is rarely one of the permitted uses.