"以死亡为主题的" can be translated into English as "death-themed" or "centered around death".
"Death-themed" is concise and directly conveys the idea that something revolves around or is focused on the theme of death.
"Centered around death" provides a slightly more descriptive phrase, indicating that death is the central focus or theme of whatever is being discussed.
Both expressions are appropriate depending on the context and the level of detail desired. For example:
"The movie is death-themed, exploring the psychological impact of loss."
"The exhibition is centered around death, featuring artworks that contemplate mortality."