Here's a dragonish variant of the ouroboros.
And here's one where instead of a simple circle, the serpent is twisted into an infinity symbol.
I prefer the infinity symbol to be horizontal, but I have yet to see an authentic ancient or medieval example. This one is a tattoo design.
And here's the dragon version combined with the horizontal infinity version.
Another tattoo design.
This one is my favorite.
One of the inns found in my Wessex setting is called The Turn of the Wyrm.
Something like this decorates its sign.