>- to, że chodzi o obrazy literackie
Yes, madam.
>- wątpliwość, czy śmierć występuje w j. ang. w l. mnogiej?
Death is one. "Deaths" is merely a plurality of instances of the same, technicalities aside.
Which is more powerful?
"That caused thousands of deaths" or "That caused death"?
>- może lepiej zamiast writing - works?
Since he wrote, say writing. Had he painted, you would say painting.
>- czy "of Adam Mickiewicz" jest lepsze niż Adam Mickiewicz's?
...in Adam Mickiewicz's writing. He owns it.
Now a bonus.
There is nothing wrong with "portrayal" or "portrait" or "images."
But just look how much more dramatic less can be:
"Death in A.M's writing."
Heck, and how more demanding.