An older piece I'm honestly surprised I didn't add here, yet.
After seeing an image uploaded by sreido on DA consisting of Steven Univere's Crystal Gems dressed like the Powerpuff Girls, http://sreido.deviantart.com/art/Powerpuff-Gems-520328... I decided to take my shot at the other end of the spectrum and draw the Powerpuff Girls as the Crystal Gems.
Of the three puffs I'd have to say I like Blossom as Garnet the most, the outfit just really seems to work for her.
Before anyone says "(insert PPG name here) should be (insert Gem name here)" I made the casting by way of whose outfit's color in the original pic matched the most for each puff, thus Blossom is Garnet, Bubbles is Pearl and (by process of elimination) Buttercup is Amethyst.