Maybe rotate the battery connector another 180 degrees? Currently, the wires may interfere with the mounting bolt.
The mechanical drills of your X1-X7 seem to be non-plated? You may want to change them to plated through holes to add mechanical support to them. Unless they are plastic? Then the non-plated holes makes sense.
As already mentioned, the ground plane doesn't seem to be connected to ground. There's some "dead copper" that should be dealt with. Either remove the dead copper, or add vias so that it's no longer dead. (For example, the area where the R20 designator is).
Move as many non-GND tracks to the top layer as you can, and if you have tracks on the bottom, keep them short. Avoid long tracks splitting your ground plane.
If you use a GND fill on both top and bottom, add some via stitching. At minimum, I'd add a GND via next to each SMD GND pad.
Double-check the drill diameter of the mounting holes. They seem large.
It's always suggested to avoid acute angles of tracks (acid traps), though my understanding is that it's less necessary these days. You have one on the bottom under MCP6004.
Add some indication of pin-1 for your 100mil pitch connectors: a line/box/arrow on the silkscreen, or a square pad for pin-1.
Even if I don't plan on automatic pick-and-place assembly, I'd tend to add fiducials to the layout.
Add board info to your silkscreen, for example the board name, revision date, and your name.