Minecraft 1.8.3 mushroom island seed right offshore of grassy taiga forest
This particular Minecraft 1.8.3 mushroom island seed starts off in a grassy taiga forest without and snow. Right nearby there's water, going across in the right direction leads right to the mushroom island. There's lava pits, water pools, a tiny bit of dirt blocks (bring saplings), plenty of exposed coal, and a few little cubbyholes to build houses in.
The seed is: 7773115691844086136
The Minecraft Mushroom island 1.8.3 can be found at x15 by z250. To see in-game coordinates press f3 on the keyboard while playing.
The taiga might be worth exploring as well.