MIUI 7 comes with New themes if you didn't get and you are right place.
You have to flash MIUI7 v5.8.22 only after that you can flash ota files
1. Make sure you have ROM zip in your phone.
2. Then Reboot to recovery.
3. Select wipe option.
4. Now Select Advanced wipe.
5. Select wipe dalvik cache and cache only then swipe.
6. Then Flash Rom by going back and choose install option.
7. Now Reboot.
You will get MIUI 7 themes and mi store app.
Note : your apps and data will be saved.