Some people use $\langle \cdot \rangle $ as a shorthand of $\text{span}$ (e.g. the German wiki), i.e.
$$\langle \{ v_1, \ldots,v_n \} \rangle := \text{span}\{v_1, \ldots,v_n\},$$
yet the notation seems to be suboptimal due to its similarity with the inner product.
Is there any handy notation for $\text{span}\{v_1, \ldots,v_n\}$ which doesn't conflict with any another notation in linear algebra?
Here is what I've tried: $[v_1, \ldots,v_n]$ seems to be simple and vacant.
None that I know of. This is not really an answer but I have no reputation to comment... The $[v_1,...,v_n]$ is bad in particular when $n=2$ since it could be confused with a Lie bracket. (And for higher $n$ with higher Lie brackets.)
Edit: I sometimes use/see used $\mathbb{K}\{v_1,...,v_n\}$. But it doesn't save many letters.