Well, pond snails are considered pests because they eat plants. Put some fast growing plants in and you could call it food.
I'm new to this so there's probably a lot available I have not seen, but if you are going for striking appearance... well, snails are not exactly know for guest appearances on late night talk shows.
Apple Snails can get pretty large, occasionally come out of the tank, and probably are among the largest readily available.
Nerites have some good size and color, e.g. the zebra. They are about 3-4 times the size of ramshorns. They generally won't breed unless you accommodate water type.
Malaysian Trumpet Snails spend a lot of daylight under the substrate but have a great, long, often colored shape (but are not very large).
Google "freshwater snails" and look around to find something you like the looks of.
You might also consider having something to go with the snails, to add a bit of interest. Shrimp, Crayfish (also tear up some plants) are interesting invertebrate alternatives if you don't want fish. I keep ghost shrimp and snails together -- they will eat snail eggs but won't bother adult snails.