Prefer the white backgrounds over the black. We liked #31 the best of your designs. Like the curves over the words and the train coming into the dash. The train obscures the dash. The dash should be more identifiable as a dash since it's part of our domain name.
#75 & 76 are interesting but we prefer your other designs better. I can see that you tried to 'evoke' an abstract train with the top part of the image. Would it be possible to take your #55 and make that train more abstract?