This is an additional question to one which I had asked on UXSE for making the Badges inclusive by providing unique icons for Gold, Silver, and Bronze Badges.
Are there any universally accepted icons of the same?
A simple internet search will tell you no, there aren't universal icons for these 3 badges / tiers. Some will use stars, some will use coins, others will use other shapes depending on: context the icons are being used for, style, preference, etc.
The one (sort of) consistent element is color: yellow-ish for gold, some shade of gray for silver and a shade of orange for bronze.