One of the best sights along the Seawall in Galveston is the Pleasure Pier. If you have been, and are missing the view, you can check out the surfcam. It will remind you how nice it is to have the opportunity to visit in person.
This is a little more than a souvenir shop on the Seawall, although you can find lots of fun stuff here to take home as a reminder of your trip to Galveston. Murdochs has an awesome deck where you can enjoy a drink and the Gulf breeze while sitting in one of their rocking chairs. It is also a great photo spot for the Ferris Wheel on the Pleasure Pier.