Ability to change team initials / short name.

For example if your teams start with the same prefix, the initials are going to be the same for all of them.

Furthermore you may want to set it manually, or if the name is made of multiple words, use the first letter of each word as initials.

This is also related to https://mattermost.uservoice.com/forums/306457-general/suggestions/15465123-team-icon

Idea is to be able to differentiate teams easier :)

I also don't know about mobile apps, but in the web version on desktop the initials could potentially include up to 4 characters.