Here's the DTE mats I created for this picture. My goal was also to create materials that aren't too difficult to render, so I looked for rendertimes along with the mats themselves. I must admit that I'm very grateful to Zhann for this idea: playing in the DTE was lots of fun, much more than I thought!

The renders of the mats are: upper sphere with AA normal, lower sphere without AA (to better show the details that the AA pass often washes out). Rendertimes are referred to 550x440 with default settings. They don't mean too much, but are useful to compare the relative render cost of the single mats.

Material #1: Worn metal, used for the pillars of the Arena and the scaffolding of the rightmost octagonal building. RT 26 seconds.

Material #2: Concrete (sort of). Used for the rightmost wall of the Arena. RT 14 seconds.

Material #3: Another worn metal with channel-driven reflection. Used for the structure that holds the Tetris pieces. RT 18 seconds.

Material #4: Rusty metal. Used for the talons gripping the Pieces up above. RT 24 seconds.

Material #5: Opaque metal. Used almost everywhere with color variations: from the HiScore panel to the Tetris pieces, the chains and the balconies, the tripods and the laser cannons etc. RT 15 seconds.

I used Adamite's iridescent mats on the cables near the ceiling and the disintegrating first row of Tetris pieces.