A band called Bring Me The Horizon already used the Flower of Life as an album cover. Many fans were enraged by this, thinking that Coldplay copied them, but the Flower of Life has been around for hundreds of years, so technically Coldplay didn't copy them. The album artwork would still seem a bit similar if both albums had a simplistic background though. (The album by Bring Me The Horizon, Sempiternal, has a relatively simple background) Also Coldplay might have been going for a creative/interesting album theme to display the colorful mood. Also the album artwork sort of reminds me of the music video of Life In Technicolor ii for some reason.