Please understand, first of all, that my tone here is not meant to be snide. I'm trying to be very clear about my reasoning.

In my opinion, it is unrealistic to ask a bunch of strangers for punishment ideas, and here's why:
1. We don't know you. This means we don't know your limits, your desires, your abilities, your strengths or your weaknesses.
2. We don't know what your relationship is like. This means we don't know if it's a TPE, online, long-term, open, etc, or any combination of the possibilities.
3. We don't know your master. This means we don't know if he's genuinely trying to teach you a lesson that you're missing out on by asking others to do what he's asked of you, or if he's just lazy and can't be bothered to figure out something suitable.
4. We don't know what happened. This means we don't know the severity of the situation within the context of your unknown relationship, and we don't know what lesson is trying to be taught- punishments are about teaching, so something blind like, "You should stand in the corner until you feel sorry," does little to address what actually went wrong and makes it even less likely that you'll learn anything valuable.

What I can tell you is that if this scenario happened in my relationship, I'd approach Him about it and confess that I was struggling. I'd open up a dialog. That's my best advice to you, if you can't think of anything. I hope this helps, and I wish you luck!