How i can change the Staff Icon

[Canapin (Coin-coin le Canapin)]

Not sure if that can help, but maybe you can have a look at this:

Replace Discourse's default SVG icons with custom icons in a theme

You can replace a Discourse’s default SVG icons individually or as a whole with your own custom SVG and override them within a theme or theme component. Step 1 - Create an SVG Spritesheet To get started, you must create an SVG Spritesheet. This can contain anything from a single additional custom SVG icon up to an entire replacement set of hundreds. The spritesheet should be saved as an SVG file. In principle, you are nesting the <svg> tag contents from the original SVG icon file into <symbol> …

Introducing Font Awesome 5 and SVG icons

See also: We're upgrading our icons to Font Awesome 6! We will shortly merge into master a branch that upgrades Discourse to Font Awesome 5.5.0 (the free version) and switches to using SVG icons instead of an icon font. This is a substantial change, with lots of benefits, and one significant change for developers. Here is a quick rundown of the changes: using SVG icons will provide crisper icons, better for accessibility and easier to customize, see this Github article for more details since…