A way to put existential ethics I think this thought of the image is something which existentialists attempt to stop. Isn't conforming to an image of yourself a good description of inauthenticity? You aren't
being, you're cognizing who you are and acting from that. Sartre's description of the waiter seems to fit that description. Rather, it seems the existentialist wants us to be who we are rather than conform to an image of who I am, in accord with a role with such-and-such responsibilities and privileges.
At its broadest I think that existential ethics are possibly consistent with a religious life -- a life of death-and-rebirth, in a sense, gets along with how wide the existential condition is. I think that this point of contrast is good because I think that the existential religionists reinterpret their religions in light of existentialism (perhaps this is a way of filling out the existential ethic?) And I like your contrast between the death of the self with life-affirming (self-affirming?) themes in existentialism. There's something to that.
Perhaps the religious life sees an end-point -- to act out of universal love, as opposed to from the self. An atheist existentialist would say that such a condition of universal love does not exist
due to moral rules or religious teaching. These too are images. Or, at least, if we are the saints that the religious talk about, we have no need for moral codes or injunctions from religious leaders, and no amount of social pressure will turn us into what we aren't. It's not the code doing the work, it's the person being who they are! We apes are partially saintlike, at times -- though not all of us.
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Or, being who they aren't? funny thing here -- if who we are is what we do, then whatever we do we are who we are, but there is the theme of authenticity -- we can be ourselves authentically or inauthentically. For Heidegger he seemed to contrast authenticity with everydayness or being busy. Interestingly to the charges made here, if we include Levinas, then I'd say he actually manages to escape the charge of selfishness or individuality, given that we only come to know ourselves as ethical beings within the face-to-face relationship of the Other.