The third update of FBS is an ability to upload your own SVG charges. Careful, there might be bugs - vector graphics are fickle. It's recommended to have one shape, without overlays. Border width doesn't count (if you want contour, transform lines to objects).
There are some premade shapes too, like 50 stars of USA or Canadian maple leaf.
Added layers now has option of transparency.
You can join the Discord to discuss FBS: https://discord.gg/StwnxP6