While I wait (impatiently) for Stronghold Games, Richard Hamblen, or whomever it is that intends to re-publish and expand Avalon Hill's Magic Realm, I'm having fun imagining what I might do if I put serious effort into an expanded game.
I've got four ideas for additional tiles: Hills (above), Swamps, Forests and Ruins. Hills and Swamps would be for travel and human and minor monster encounters. Forests and Ruins would be for Monsters and Treasure sites.
The Hills tiles (Gorge, Ravine, Abyss, Defile and Crossroads) are similar to Valley tiles, but have some difficult terrain in the form of a Hill in one of the two travelling directions. The Crossroads tile serves as an alternative character starting point, if one does not want to start at the Inn, the normal starting location.