Virtual display for simple GPU development
An alternative would be to use PLI/VPI to call out to some C code - so rather than doing the top level pin driving, call a system task that stores the pixel in a software frame buffer and renders that to a window.

I've used the same technique for a UART recently - instantiated another uart with the TX + RX crossed over, and when the one in the testbench receives data - feed it to some C code with a system task that writes to a PTY (and vice-versa).

Given that the simulation probably won't run that fast, writing image files or binary data then post-processing might make it more useful.