I want to collect some feedback and suggestions before making the design of 3rd level of my game named 'You Run!'. You can view more info about the game here: http://www.gamedev.net/blog/1865/entry-2259968-you-run/

So, what you would like to see in a level of an endless running game? I'm currently making 3rd level for my game. So I want to get some suggestions from you before making the level. Should it have buildings? should it have grass on ground? should an AI character run behind the player? How the game should be? What type of scene it should have (nature, indoor etc.)?