The orientation and placement of the sensor do not match the recommended orientation given in the datasheet (page 7).
There is no cutout under the sensor so there is no way to mount the lens. See page 9 in the datasheet.
The placement of the USB connector could probably be changed. It should probably be placed in the front of the mouse at the edge of the PCB. Could probably be a bit awkward having the USB cable sticking out the side of the mouse.
The decoupling capacitors could probably be placed even closer to their respective pins on the MCU. I don't know if you remember Henrik's lecture about lab 2 but he started with the decoupling capacitors and placed them as close as physically possible to each pin.
When I run the DRC I get a couple of "Track too close to pad". The Motion and SCK vias are touching the C7 capacitor.
Nice job overall! I thought about a few things:
Other than that I think it looks pretty good!