This is definitely an interesting question!

I would have thought your best bet is if you pick some physical sign that you don't really have any prior association with, a random animal would probaly work well. And then in the hour or so before going to sleep look at some pictures of this animal or read about it odds are it will show up in a dream. Usually the content of our experinces in the last hour or so before going to sleep heavily influence our dream content that night. Because the experince of this animal will be novel to you, your brain will need to form new assoications to it (which it will proceess while sleeping) and so it shouldm't be overlooked in your dream content like with your religous emblem.

Also since the animal would be external to you whether you view yourself in the third or first perosn within your dream shouldn't be a problem. It might also be helpful to repeat some kind of phrase like ' whenever i see a (insert animal name) i know i am dreaming' while looking at/reading about the animal beforehand.

One more thought if you do this over a few days it would probably help to always look at/read about the animal in the same situation before bed, e.g. in a particular chair. That way you could ammend the phrase to 'whenver i see a (insert animal) and am not sitting on my bedroom chair I know I am dreaming'. The idea is to create an enivornment where no matter how or where this animal shows up you can know it is a dream expect for the very specific circumstance you are using to induce the dream content.

Hope that helps and good luck!