1. When Shaw's expedition finds the first Engineer decapitated at the Urn room's door, why did this particular Engineer seek to go there? Was it an accident or was the individual Engineer trying to get into the room before he died? If so, what could the room have been to him?
2. When Shaw's crew get into the Urn room they notice that in addition to the Urns, there are two separate images: the great Face and the Xenomorph mural. Ridley's treatment, lighting and decoration of the Urn room immediately has the feel of a holy place. If so, the Face could be a image of their God depicted as a perfect physical specimen of the Engineers' race. This depiction may indicate not only Order and Unity, but a strict adherance to a certain asthetic or racial standard.
The other image, the Xenomorph could embody Chaos and the misuse of creative power and its terrible consequences. After all, what Church is complete without an image or two of the devil and the damned?
As to the urns themselves, why were those few there? We see, later in the movie, vast stores of the urns in another compartment. So the idea of basic storage is ruled out. It may be that the first Engineers may have placed them before the images as either an offering, to be blessed or for ready access for use.
It all depends on how you look at the movie I suppose.