Here's a design I came up with a little while ago. These two are Onyx and Spade. Onyx is the green dragon with purple spikes, and Spade is the dark grey and orange dragon. They're surrounded by the Onyx "O" logo. So who are they? They are two primary characters in a series of novels I'm currently writing called "Onyx The Half Hero Dragon". I'm very far into the first, and I'm already getting some solid ideas for the second. There will be a total of four books.
You can see a larger image of this on my DeviantArt account.