We need more flexibility with themes in the web version of the mail (tbh in desktop apps i would like to have this ability also: at least to use web theme inside the app without settings for it). Look at the attached image — I really like how one of the services lets you choose a theme and also set accent colors.

Currently, we can change the mailbox color scheme or select ready-made themes, but it would be great to also apply custom colors to these themes. Sometimes it’s fun to have a Christmas or Halloween theme. Ideally, there could be a “Seasons” theme that automatically changes the interface with seasons and holidays.

This is more of a nice-to-have feature, so it could be limited to paid subscribers.