NOW THAT IS ONE HUGE BUTTERFLY!!! My favorite. Good job!

nic 1....

Nice idea, I bet they would have to tell each other a lot and good choice for the background, it adds a dreamy feeling to it.
I have a few suggestions on how to improve it
The train and the butterfly are both very pixelated and blurry in the high res. I think it would look better, if you'd replace both with a less pixelated version. You also forgot to cut out two white parts from the background of the butterfly. Next to the front legs and between the body and the legs. And maybe you could also think about the position of the train on the tracks. The "wheels" (no clue, how the English word is) are not on the track at the moment. They are pretty much directly in one line with the white lights, so it might look better, if you either make the train bigger or the tracks smaller. If you wanted it like this, just ignore that part
Good luck!

Thanks a lot for this suggestion, Elke ! I'll work on it as soon as possible

EDIT : I made some changes

It has a nice vintage feel to it. Nice

great work author...very nice mood...vest of luck