Nice work, can we get a picture of the back side maybe?
UV-LEDs? Did you actually go full out photo printing on your PCB? Most people doing PCB's in the home use toner transfer. I personally would like to go photo printing myself. I really need fine pitch traces for some of my planned projects, but the investment cost for a full high resolution photo PCB printing setup is to high for me. With the cost of good quality LASER printers staying really high, I'm probably going to be left only able to use breakout boards.
Anyway, moving on...
Now correct me if I'm wrong, but you are going to light one horizontal row at a time, starting at (for instance) the top, then going down to the bottom? Meaning one full screen refresh cycle will consist of 8 "steps", where each "step" turns on or off any number of 64 LED's for a set time? If so, then the way you have the setup now is perfect, and you should see consistent brightness across all LED's without having to resort to changing the duty-cycle based on how many LED's are lit.
If however you were lighting each column at a time, then you may run into significant differences in brightness depending on how many LED's you light up. This is because all LED's being lit in a column have to share current through the one resistor, but just one LED will git all the resistors current to it's self. If this was going to be an issue it would be an easy fix in software, one would just use a shorter on time for lighting single LED's. This may also require the use of the output enable pin on your shift registers though.
It's better to do one row at a time anyway, much much faster and more consistent and reliable LED performance.