Hi, Sorry for the late answer, didn't see your message earlier, we're all busy with the jam :P You will have faster reply if you join us on Discord!
Yes you can modify the mandatory symbol as much as you want to make it look what you need.
Just a small warning however: it still has to be easy to identify by the Judges when they will play the games (they might not want to spend hours in every game looking for a hidden symbol). If they don't see easily that your Ouroboros is the 2 arrows symbol, then they will think you didn't respect the theme.
Also it depends if you want to win a prize or if you participate just for fun! Indeed we highly encourage creativity, so just do something that you are happy to do!