The current flag of Alagoas offers (too) many symbols that could be reused. I chose to go with the fishes and the castle, but there's also the water, the rocks, the (fat) star and the flowers around the shield. I don't particularly fancy stars on a flag, since too many flags have them already, greatly reducing their usefulness as an identifying symbol. The castle, however, is much more uncommon. My biggest concern about it was that it would be ugly - but I think it turned out just fine.
The current flag of Ceará looks just a bit too much like the flag of Brazil to me. Therefore the colors had to go, but I maintained the global layout (a horizontal diamond shape with a circle smack in the middle.) There were plenty of colors to choose from on the shield. From the symbols on the shield (sun, tower, bird, mountain, boat, windmill/tree (?)) I chose the boat, symbolizing Ceará's connection with the sea.