A preserved animal keeps the look of life without the life itself, so it is read as clinging to a moment or a past that has already ended. Dream books see it as a wish to stop time, not as any omen.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.