Do you save them in "C:/.../Warcraft III/Maps"? If not then that's why they don't show up. If you do then the map-name is too long (or, at least that's what I've heard) What I do is make a new folder for the maps I make in "C:/.../Warcraft III/Maps/MY MAPS" so that they DO show up.
We all know that there is a filesize limitation of 8mb for multiplayer games on Bnet as well as in LAN games.