I think I know where the common error is. The map feels too open and the use of placing props in areas, such as that lovely picture, you are doing so in order to break up the huge lines of sight that does not feel as blatant when compared to physically modifying the real layout, in terms of changing the brushwork and empty space to your own liking. I suppose it's an easy habit some people are going to have to avoid, and grow used to in terms of this contest. I think I may also suffer from this too.
I have to agree that there are huge lines of sights in this map that are going to prove themselves rather difficult to work with, but even though that is a really nice and visually pleasing method to break up the combat in that area, it would quite clearly change the flow dramatically. New sentry spots, cover from Snipers, sticky-bomb spots etcetera. Captain obvious perhaps, but it's quite clear you're finding it rather difficult to refrain from making such game-play altering changes.
I don't really wish to be the only one prepared to say this on his own, but since no-one else appears like they're going to, and given your earlier post in this thread, in which you expressed quite a strong dislike for the layout itself:
Perhaps this contest just isn't your "cup of tea" so to speak?
That the layout and the rules are just too restrictive to work on without tripping up with every few changes you make? I think most, if not, all of us can see what you're doing, don't get me wrong, it looks great with what you've done in terms of detail already, it's just that your sub-conscious absolutely hates the layout, or at-least dislikes it to some degree, as many others do too. Therefore you're making subtle changes you would like to have seen in the default layout without really realising it, yet the rules are preventing you from doing so.
I don't think you should give up by any means, but I think you may find it hard to restrain yourself from making these changes from often cropping up as you work on it, given this is only just the very beginning of the map itself.
Just my opinion.