Hi,
By "single side" I mean one (1) side of copper on the PCB.
You will notice you have 95% of the tracks/traces/fills on the red side.
I can see several oportunities to push some of the blue ones to the red side.
All of the "through-hole" components already only have a trace on the red side.
This means that if the patterns for these devices are flipped over you can install them from the blue side of the board.
This means you can save on the cost of the PCB.
If there are some locations where you just can't get around using a track onm the blue side you just use a wire link or 0-ohm resistor.
Another thing I forgot before:
Is the 2 pin component near the bottom left corner the power connector to the board?
If it is you should have a more direct (lower impedance) path from it to your ground plane fill, not the circuitous path that you have now.