Scenery towers can be useful, but they can also be overused. For example, in Marble Blast Platinum, scenery structures are usually added for more reasons than simply to make levels look good. For example, many Easter Eggs are hidden by or on top of the towers (for example, Jump Tutorial, Flight of the Marble, Uphill Racing). They can also be used for alternate paths and shortcuts. But if the towers are just there and do not serve a real purpose in the level, I would advise that you leave them out. And different levels should have different towers. For example, the towers in The Ultimate Friction Challenge are made of ice to go along with the levels theme. So I recommend that you use towers that fit the theme or color scheme of the level.