Presumably most of these are accidental, which makes that an ill-fitting term.
Is narcisside better?
It seems okay. It would roughly translate to selfie-kill which is good enough for killed-by-selfie.
Why does being accidental in nature make it an ill-fitting term? Suicide is not the only word to use the -cide suffix: genocide, regicide, homicide, uxoricide. The -cide suffix regards the act of killing, not of intention or purpose.
Suicide is defined as intentionally killing oneself.
But selficide refers to the -cide suffix, not to suicide.
But then again the "self" prefix means doing it to yourself, as in "self-portrait" (which is where "selfie" comes from): taking a portrait of yourself.
So "selficide" would mean killing yourself, i.e. the same thing as suicide.
No! It means the selfie killed you? Which would make it correct.