as i answered by mail already 
…you should simply wrap your snap app around the original omxplayer-pi source and utilize it internally from a wrapper script or some such … the omxplayer-pi source is at:
https://github.com/ogra1/omxplayer-snap
and an example how to use it with some tool wrapped around (here two small shell scripts and a html page that create an IPTV player fo german TV stations) can be found at:
https://github.com/ogra1/iptv-player-snap
that should give you some impression how to create a snap that includes omxplayer as a backend …
i’ll eventually add a service to the omxplayer-pi snap itself that you can manually configure to do simple tasks like looping a video automatically or stream a single webstream automatically right after boot.
and for future debugging … to get more than “Have a nice day!” out of the player when something is wrong, you can just add switches like -I, -i and -s to get more info … (if you run omxplayer-pi without any options/file or with -h/–help it will print its help page for all possible options).