To make a custom sticker:
Add a spot
Click on the smiley face
Go to “more”
Upload your own image
Then click on the outline emoji to see different styles
If you upload an image with a transparent background, then you’ll see it “cutout” / “sticker” style, when you click on the cutout icon (next to the trash can)
To easily remove a background from an image:
On Mac, go to Finder
Right click on an image
Click “Quick Actions”
Click “Remove background”
Otherwise, use a service like remove.bg
Removing a background on a Mac
How to add logos to a map: