I think if it makes you feel better, then do it. Especially if it elicits positive feelings.

I had commented earlier about this - but I found a great link to show what I was talking about ...

[viralnova.com]

I don't like the idea, but I won't stop people doing it.

I might be the wrong one to ask , as I take weird as a compliment.
sounds ok to me. In fact, many years ago, portraits of dead people - dressed and propped in chairs, were a "thing" !

If you took a pic of him while he was alive could you have told the difference? Would the camera have captured his breathing? Don't sweat it and don't discuss it further with your sister, it's her issue and not yours.

No you're not weird. I would have shooed everyone away though because it just does not occur to some others how other people mourn.
My Mom & I did this with my grandmother.

No,go home and create some memories on a CD(several), the Human memory fails over time, printed pictures fade from light exposure,and handling. Your Daughter may reconsider with time.....

I’ve not yet had that opportunity … and decided recently, far away, I’ll not likely attend.. Creepy replaced by sad?

My mother took some of her mother, I think it’s fair.

It was the thing to do in the 1800's. If you love someone and want one last picture, go for it.