This is a collection of some of my additions to the field of counting trains with trains.

Simplified cascade

This is a simple way to cascade more counters to get more digits. It does not require one edge detector for each digit, only for the first. The idea is to let the green pulse from the edge detector get through to the next counter only when a digit is at 9.

Inverted counter

If you have built a counter with outputs and added NOT gates to all of them, then don't be mad at me for writing this. The following counter design has inverted outputs. The transition from one state to the next is through all red, which makes it suitable for a 7-segment display. The train has a total length of 37. You should probably use multiple engines. Another option is to have 9 small trains, but that requires some more signals.