Item Frame

The Item Frame is an item similar to a display case. It displays the item or block that is inside it. Players can place items in the frame by right-clicking while holding the item. The displayed item can be rotated by right-clicking the frame. Maps show their contents, and compasses and clocks work as normal. When broken, the frame drops both itself and the item it contains. Because item frames are technically entities like paintings, they can be broken in Adventure Mode.

Uses
Item frames have many uses, and can be placed on cactus blocks, pressure plates, fences, Trees, slabs and cobblestone walls, along with all solid blocks. The player can place items into item frames by right-clicking with the held item in hand.

The player can use item frames to hold items for convenient retrieval or reference, instead of having to open a chest or dispenser to retrieve or verify specific items. This means item frames can be used to label chests, dispensers, etc. This also allows working clocks and compasses, as well as maps, to be displayed against a wall. A map put into an item frame will show markers at any other item frames with maps in them. This is a good way to mark certain areas.

A Book and Quill can be placed inside an item frame and will store all writing inside the book. This feature makes the item frame useful as it saves chest space and creates a nice image.

Item frames can be used to display crafting and brewing recipes, and can also be used to hold fire, allowing for safer fireplaces.

Since items in the frame can be rotated, this allows for directional pointing using items that are shaped like pointers or wedges - such as arrows, tripwire hooks, flower pots, redstone, etc.

Since levers, torches, and buttons can be placed against the item frame, this allows for color-coded levers (using colored wool), decorative torch holders (using slabs or trapdoors), and decorative gold trims for buttons (using an item frame inside the item frame). Item frames can be used similarly as signs, allowing for decorative armrests for chairs.

Item frames can be placed against piston heads to make better-looking frames.

In Creative mode, items can be cloned by placing multiple copies of the same item in different frames. This is a handy way to clone enchanted weaponry or tools although items can only be retrieved in Survival mode. It is also possible in Creative mode to place multiple item frames on the same block after restarting the save. This allows the player to stack items in the "same" frame by placing an item in the frame, saving/quitting to the main menu, and restarting the save. After restarting, it is possible to place another item frame on the same block as the existing one, and the player can then place another item in the new item frame (the first item cannot be rotated after restarting the save). This can be repeated multiple times unless the entity limit is reached.

Bugs

 * Torches can be placed on item frames, but only indirectly (possible feature).
 * If the block an item frame is placed on is moved by a piston, the frame will not move. However, the frame will break upon walking into it.
 * When placing an enchanted item in the frame it appears unenchanted.
 * If you put more than one item (in a stack) in it and mine the frame you will get only one of the item back.
 * If you have an item frame on your field of view, mobs will sink through wooden planks (but not wooden slabs).
 * When more than one item frame is filled with the same map, only the first map is marked on by a green marker, as opposed to both of them (may be intentional).
 * You can place multiple item frames in the same space by right clicking the space around the frame on the same block.
 * When you place an item frame in a item frame sometimes you only get one item frame back. (I have only tested this in survival)
 * You can put an item frame on top of any non-solid block (such as a lever or brewing stand) and they will overlap. The collision box of the item frame overrides that of the original block, so items like buttons with small boxes will be completely hidden behind the item frame's making the button unusable.

Trivia

 * The item frame is based upon a suggestion on Reddit, like the Ender chest and flower pot.
 * Item frames can occupy the same block as water without popping off.
 * Items appear flat in the frame while blocks protrude from it.