How to use these stickers: first, you'll need Trello gold to use these. 

1. Inside any Trello board, open the "show menu" option and select "stickers".
2. Scroll down to the circle with the plus sign and click that. 
3. Highlight the stickers and select "open". 
4. Viola!


Credits where they're due:

brain and headstone icons by https://www.flaticon.com/authors/smashicons from their halloween pack, available here https://www.flaticon.com/packs/halloween-52

Zombie brain icons created by Moodthy Alghorairi. 
