Custom styled Icons

You can always upload your icons as documents, then utilize a!documentImage() to display them.  If you have a specific use case, feel free to share it here.  

I would like to use them in a a!buttomWidget. How ? 

a!buttonWidget(
label: "Submit",
submit: true,
style: "PRIMARY",
icon : "???"
)

For that you'll need to use one of the official icons.  A workaround that's sometimes usable is using the "card as a button" pattern where you take a Card Layout, fill it with whatever you want (including a document image), and make it clickable like a button.  There are obvious limitations to this approach, though.

For that you'll need to use one of the official icons.  A workaround that's sometimes usable is using the "card as a button" pattern where you take a Card Layout, fill it with whatever you want (including a document image), and make it clickable like a button.  There are obvious limitations to this approach, though.