I'm going to point out an article and make an additional suggestion, then ask a question of my own for any who might read this:
First, there's an article in the November '04 Finescale with a great technique for making displays for waterline models. The author used a wooden craft store display base, and used aluminum foil, spray paint and Modge Podge decoupage coating to make the water. Great article.
Second, in his book about building scale aircraft, Paul Boyer sets one of his models on a picture frame. He took the acrylic pane from the frame, painted it with a concrete color, drew slab lines on it with a black marker, and placed it back in the frame. Not as useful for ships, perhaps, but maybe it could be helpful if you're doing a waterline ship.
Lastly, here's my question: What's the best way to label custome bases, especially if you're on a budget? I'm not in any competitions at this point, so all I'm looking for is something that looks good.