Telegram Desktop ThemesTelegram Support
Since version 1.0, Telegram Desktop supports Custom Themes, so you can have an alternative design of your app.
All theme-files have the .tdesktop-theme extension. You can find more themes on https://t.me/Themes
Note: To use themes, make sure you are using the latest version of Telegram Desktop as themes are supported from version 1.0.
To check your version, go to Settings » Check version under General
If your version is v0.x.x, click on "Check for updates"(if the update is not yet downloaded) or "Restart now" (if the update is downloaded already).
To contact Telegram support, go to Settings, and scroll down until you see the 'Ask a Question' button at the bottom.
If you want to join us, check out the Telegram Support Initiative.