This screenshot, ' Tyrant under glass ' was created under Microsofts Game Content Usage Rules using assets from Halo 3, © Microsoft Corporation.
Please read these conditions in full that confirm such images may be distributed, following certain rules, at the following location. [link]
If there is anyone else wanting to post such images on dA, then as long as you post that little disclaimer, you are legally covered. You have followed Microsofts conditions to the letter.
I love all the cool stuff you can do in Halo 3.