Can other ESP8266 Code be loaded onto the pixelblaze?

Specifically I’m thinking of WLED it was just a random thought I had while discovering all the things the esp boards can do

The ESP8266 can be reflashed, but it overwrites the Pixelblaze firmware. You’ll need an external programmer, which can be made from a 3.3v usb serial adapter, and a button. You’ll need to back up the firmware first if you want to go back. Its not the easiest, but doable.

The expansion header has all of the pins necessary for flashing.

Before trying it, you probably want to be sure that the hardware is compatible. Make sure that the image you load is using a pin that goes to the level shifter, by consulting the schematic and comparing to what WLED supports.