This is one of my personal favourite mods for Minecraft 1.2.3, and it should definitely be implemented into the game, it gives you a great way to showcase things you are storing away. Instead of putting your items into a chest and then having to explore the chests to find all the stuff, you can have them on shelves to find them easier and it looks cool!
The shelves look like wooden stairs, but they have items on top if they have things in, the only down fall of having shelves is they only display items 3 x 3 so you can showcase 9 items. Maybe do it with your valuable items. Completely up to you but I love this mod!
How to Install Shelves Shelf Mod for Minecraft 1.2.3
Download ModLoader
Download Shelf Mod for Minecraft 1.2.3
Open .minecraft / bin
Open Minecraft.jar
Delete META INF
Drag mod loader files into Minecraft.jar
Do the same with the shelve mod files
Done!