For a couple of years Brave has been my browser of choice. I hate ads on the internet and I believe it is not actually possible to browse any website without an adblock. Of course I could use any of the available browser extensions to block adverts or even use something like Pi hole, but I like to use tools that have useful features built-in and have sensible defaults (this is also why I use Zed code editor instead of Visual Code).
Well, actually – Brave might not be the best when it comes to sensible defaults, I always turn off stuff like sponsored backgrounds, news, AI/web3 stuff etc.

The problem
Brave doesn’t actually let you set custom avatars, there is a feature request from 2020 to add option to do it, but as of today — it’s still not implemented (and it doesn’t have too many votes).
If you read through that feature request — you probably saw that someone already answered the question on how to customize your avatar, but nevertheless I will also show that here, as my article about Japanese flushes said — you can never have too much backup.
The solution
Go to brave profile management by clicking:
☰ → Settings → Get started → Profile name and icon
or by simply pasting brave://settings/manageProfile in the URL field. Next pick your future avatar and hover over it to check it’s name.
avatar_edgy_royal.png.
Now prepare your own picture and give it the same name. Original images are 288x288 pixel PNGs — but they can be smaller or bigger (personally I’ve used 500x500 pixel images and they work just fine). Out of ideas on what to use? Just download your favorite emoji or use an avatar maker.
You got your image ready, just need to copy it and paste into correct directory — depending on the OS it will be slightly different one.
macOS
Open your Terminal app of choice, create Avatars directory and paste your file there.
mkdir ~/Library/Application\ Support/BraveSoftware/Brave-Browser/Avatars
cp avatar_edgy_royal.png ~/Library/Application\ Support/BraveSoftware/Brave-Browser/Avatars
Linux
Open your terminal emulator of choice, create Avatars directory and paste your file there.
mkdir ~/.config/BraveSoftware/Brave-Browser/Avatars
cp avatar_edgy_royal.png ~/.config/BraveSoftware/Brave-Browser/Avatars
Windows
Press Win+R on your keyboard to open Run utility and type %LocalAppData% to get into your AppData/Local folder and the navigate to:
BraveSoftware → Brave-Browser → User Data
Right-click to create a new folder and name it Avatars, paste your avatar into that folder.
You did it!
You may need to restart your browser and your avatar might not show up in all windows, but it will definitely show in profile picker and in the profile icon in the top right corner.

There are plenty of webpages on how to do this and I read through them while writing this article: 1, 2, 3, 4