Stamp Sudoku

All you have to do is place the pictures in the grid so that every row, every column, and each of the nine 3x3 square contains only one occurence of every stamp.

You can solve any puzzle generated here without making notes, and they all have only one solution. If you try to place a picture where it already exists on that row, column, or small square, both occurences will be highlighted in red. If your mistake is more subtle, you can click the 'give me a hint' button and any errors will be highlighted in red, or if you've made no mistakes, a green square will show where you can go next.