Once you jailbreak your Xiaomi Box, you basically can install any Android App. But it is not recommend to do so. Because it will take you time to find the correct App for the TV screen size. I think some one has posted before, download the Sofa Butler App is one of the alternative. i.e. 沙发管家 智能电视应用市场_安卓电视软件TV游戏TV APP下载_智能电视游戏下载_沙发应用市场
Because, from here, you can download a lot of "China" Apps that is optimised for TV Screen. You usually find the App Icon has a "TV" word on it.
If you do otherwise, search the web from Google Play or Blackmarket, etc... most of the Apps are for mobile phones. So, you will get lower resolutions App, or even App that only uses mobile data. But again, I don't use Xiaomi to watch my Netflix / Hulu / iTV / Amazon Instant Video, so, may be you still can find these app on Google Play.
Hope this info help.
Found this...
Mini Liew: Xiaomi Box - Jailbreak or Not?
Use the app to load tons of TV app. Nice!