Currently deploying a Mattermost instance with custom themes (for instance, company-branded colours) requires manually patching https://github.com/mattermost/mattermost-webapp.

Admins should be able to deploy Mattermost and specify custom themes in place of the existing ones (or an addition to the existing ones) without having to patch mattermost-webapp. This could be done in a number of ways (e.g. configuration or being stored in the database), but should persist across version upgrades.

Additionally it would be ideal if admins could specify the default theme for users, as well as having full control over the list of themes available.

I've created https://github.com/mattermost/mattermost-server/issues/16658 in reference to this, fwiw.

Thanks, Tom