Here are three coins (Gold, Silver, Copper). They contain simple animations to make them stand out to the player:

Floating/bobbing over the ground

Shadow size changes slightly

Spinning

Shiny stripe flashes over the coin as it faces the viewer

Each frame is 32x32, 8 frames of animation per coin. The floor-center of the coin is at 16,28 (centered, 4 pixels from the bottom; in case you want to draw the coin at arbitrary locations instead of just inside a grid square).

XCF and Blend files (and animated previews) can be found here http://opengameart.org/content/animated-coins