My OCD for schematic design is going crazy...
just some pointers.
Input on the left processing center, output on the right.
avoid crossing wires, it makes it confusing.
for your design, fwd / reverse can be achieved with a single output, using an H-bridge.
an additional output could be used for enable / disable.
I am not sure why you have diodes on the base of your transistors? was that to give diode protection?
You will want to diode protect your h-bridge, (or transistors) and your arduino, but, that's not how its done.
here's a basic tutorial on diode protectionhttp://electronicsclub.info/transistorcircuits.htm
the arduino has no diode protection, or at-least my uno doesn't.
using source and ground labels independently instead of making loops to singular source and ground points, can make your schematics much neater.
attached is a drawing of 2 voltage divider references to the aruino. one reference shift to +voltage the other reference shifts to gnd voltage.
by comparing the difference, you can shift your motor accordingly.
by setting your voltage references in physical proximity to each-other, with a divider between the photo-resistors, you can use the casting of shadows, and movement of the sun to let your circuit auto-calibrate.