The dir contains all streamtuner2 [plugins](wiki/write+a+plugin). It's probably going to get renamed to `plugins` even somewhen, as it doesn't just contain channel tab plugins, but also feature plugins, and even core modules now (bookmarks, search, configwin).

It's still supported to supply a <kbd>*.png</kbd> per channel module. But the default ones now embed the icon as `png:` meta field.