I've change nearly all the ressources of the mi band 4. For the basic menu, I have choosen typical Stock Android App icon's, for the "more" menu, I've choosen pictograms from stock Adroid 10 Q, from Google Pixel settings and for the rest, I've took ressources from the Google Apps. I also modify the weather icons for Google weather icons. I went in the details to propose you an unique Stock Android Experience on your Mi band 4.
If you want to have this awesome theme, you have to download the file for your band below and Notify and Fitness App. Click on the file and select: Update Firmware. Then hit Start and wait. If you don't like my theme, no problem, just download the original ressources file below and update the ressources. If you have any questions, reply to this thread and I will try to answer the faster. If there is any problems or you want another version (also NFC?), leave a comment. The firmware versions are indicated in the download spoilers.