Oh that's a good question. Like your idea of giant animal footprints! You could also cut it into stars, angels, snowflakes etc, paint them and add glitter, then hang them as Christmas tree or garland decorations? You could use cookie cutters as templates.
I think your yoga mat is asking to be made into fish to float in the bath or maybe some zany drink coasters... or on a practical level, it would make a great carpet underlay or lining for a small garden pond.