Found this seed on MineAtlas and thought it had to be shared. There are 4 ... yes FOUR ... mushroom islands clustered near the spawn. Personally, I'm not a fan of mush islands, but lots of people look for them. So here is the seed: 886895402627842
Full disclosure: I have not player or even tried to load this world. So please post a reply if it doesn't look like the image below.