The images on coins can be great for world-building. Is there a ruler depicted? Does the coin harken back to an earlier time, like Charlemagne's coins? Is there a symbol rather than a face like during the reign of Louis IX of France? You can make a major comment about your world with just a one-sentence descripton of a coin's surface.
The materials and types of coins are also important. Are there quarters, nickels, dimes, pennies, half-dollars, and dollar pieces? Are there pieces of eight? Platinums, golds, silvers, and coppers? What does the material and type of the coinage say about the area in which it was minted? Maybe an area has a lot of gold but very little silver so that silver coins are worth more than gold coins. Then that silver pitcher in the King's palace seems a lot more important.
For a quick and easy world-building tool that can jingle in your pockets, look no further than coinage.