Stupid thing of the day to try on your favourite Slack channel:
1. Make an image of yourself bordered by the edge of a speech bubble. Make the image an exact multiple of 32 pixels in each dimension (this one is 128 × 96):
2. Use ImageMagick to cut the image into 32 × 32 pixel tiles, e.g.
https://danq.me/2020/10/05/slackvatars/