I mean, you mostly just need blood and skulls, it doesn't need to be fancy - like any gift, it's the thought that counts. Excess bones and bloods can be turned into glue [1] or filler material to increase the structural robustness.

[1] Glue made from animal bones is well known, but apparently you can also make glue from blood: https://www.warf.org/documents/technology-summary/P07418US.p...