I have the Birdworks Seagull kit -- it's largely foam, very nicely cut. Looks very clean and precise with a very real-looking shape. I'm looking forward to it once I get a little flying wing time in on another plane.

There was also a big (about 2 meter span) electric seagull published by RCM in 1991. (You can look it up in the plans section of their site under the name Electric Seagull). If I remember right, it was designed as an enlargement of the little tin-can seagull (a 2" or 3" span thing you cut from the side of a soda can)... as a result, the tail is an inverted V, a bit large compared to the real bird, but in the air, it looks good in the pictures.