You can wish for terrain types and dungeon features. These are already wishable in wizard mode; the justification is “If the player wants to wish for lava, why not let them have lava?” You are allowed to wish for a throne, because the chance of getting two or more wishes off it is tiny.
Add a “specialness” value to each special room and possibly dungeon feature, based on their approximate usefulness to the player. (For example, a swamp room is virtually useless to the player, a treasure zoo not very useful, a throne room more useful, and a temple or shop the most useful.) A level will start out with some amount of specialness available, and randomly chooses special rooms and features to add until it runs out of specialness.
Fountains, sinks, and other dungeon features can generate inside shops. Using them in any way incurs a usage fee. Destroying them incurs a larger charge to be paid immediately, or the shopkeeper will get mad.
Ovens, a dungeon feature (\) that you can use to cook food, light items on fire, and test potions in a safe, controlled manner like you can with rings and sinks. This happens by putting the potion in the oven and it produces some cosmetic message that can be used to identify it.
You can teleport dungeon features (except high altars, of course.)
Bed, a \ which if you sit on it makes you fall asleep for d10 turns or you have fully recovered your health. While sleeping on the bed, you get the same effects as hungerless regeneration. Found in barracks and some special levels. Breakfast not provided.
Thrones will not disappear in a puff of logic unless at least one interesting effect from sitting on them has happened.
Players can polymorph dungeon features by zapping a polymorph beam down at it, with some special cases:
