FC2, why not do a capture of a Trainz(1) item, or a take a photo of either the real carriages, or model for that matter, and use them in your signature - but make sure the photo is reduced to fit the signature limits.(2)
1. But I'm not sure if captured shots of items in train simulators break any copyright or not.
To administrators/moderators, I wonder if other captures of other train simulators are allowed to be used in signatures, especially if the item/s aren't available in Trainz, and wonder if non train/tram stuff is allowed in signatures?
2. Reducing photos/captured shots most likely means slightly sharpening them.
EDIT: Forget to say, what's the go with using avatars in signatures?
PS: What, no Red Rattlers for avatars? :'(