I guess the cube is the size of one in-game square?
the silo in itself looks good, but I think it has too much detail for xcom
I guess it is 2x2 squares, right?
About the ladder: I'm not sure if the ring-like things are supposed to be the rungs of the ladder or those railing-like things that you usually find on high-reaching ladders that are supposed to keep you from falling off. If they are the rungs, why are they convex? if they are the railings, it doesn't look like your average xcom human would fit in there. Also, I'm not sure if I would put ladders in the graphics when the game engine doesn't support anything like those. It will only lead to frustration when people see a ladder and try to make their snipers climb it only to find that it's not possible. (Now if openxcom were to support ladders, that would be way cool, but the mechanics involved might be just a little too much. And I'm not even starting on the animations...)
About the content of the silo: always consider that objects may be partially (tile-by-tile) destroyed in xcom. if somebody were to destroy just one part of the silo, the contents would be expected to spill out - but the game engine doesn't support that. so either we only use empty silos, or they need to contain some kind of solid substance that doesn't spill - which kind of goes against the principles of a silo, I'm afraid
the way xcom works, you always have to consider this tile-based segmentation. if a 2x2 structure has some kind of support structure along the side (or something like your ladder), it is best placed
off-center, contained to one of the segments. otherwise, a partially destroyed object features a structural element that has been split lengthwise, which goes against expected behavior. am I making sense? now that I read it again it reads kind of complicated...