Most recognizable of the ship designs are the ship's smoke stacks, but the fourth stack was actually just artistic in nature and served no functional purpose.
If someone in authority stacks an organization or body, they fill it with their own supporters so that the decisions it makes will be the ones they want it to make.
If you say that the odds are stacked against someone, or that particular factors are stacked against them, you mean that they are unlikely to succeed in what they want to do because the conditions are not favourable.