Everyone has to get used to "backlit" being a poorly chosen term.

It means an important part of the train does not have direct light on it.
1: visible side of train is in shadow - pretty much no chance for RP. In addition, you have it framed pretty tight. Also, RP is generally not concerned with timing and "cannot shoot" issues.
2: a significant part of the nose, in fact, all forward facing surfaces, is in shadow - a no-no for RP, particularly for a basic train-and-nothing-else shot. And much of the frame is filled by the nose.
3: Lots of extra space on the right, the engine too close to the edge on the left. But most of all, geesh, not even close to level!
General guidelines: for basic shots, RP likes the train fully lit, just the way the site is. And you are a bit of a "tight-framer," at least for my tastes.
Good luck, and welcome back! It appears that you have been away from RP for almost four years. You will find that standards are much tighter since you uploaded your three shots in 2004.
Oh, and it is easier for us to deal with your shots if you simply provide a link to the rejection page.