I think the senery,I dont know if its just pesonal preferance,but its not ofter i see a movable senery on an MLG map,and i think that Unless certian rules are obeyed,It has to be symmetrical.
um no movable scenery (as said above) unless its merged or held in place so it can't move. No equipment, power drain etc, no shotgun (except for a few exceptions) no sword no hammer. Basically just br carbine stickies and frags, and sniper if the map allows for it. Oh and very very symmetrical, a few things on map can be different but the basic layout of both or all bases must be the same, there must be equal opportunities for each team to get at power weapons and well of couse all weapons must be balanced perfectly. Thats an MLG map lol, on Competitive you can add these aspects but don't have all the rules.
Here's a guide on MLG standards, it's fairly clear what the differences are between normal competitive and MLG once you've read it.