If you have a large rectangular array of fixtures - you dont have to create a fixture for every single pixel.
You can use the 'GRID' fixture.
I have a few array sizes defined in the fixture type menu, but if you use a spreadsheet to import- then you can use any size of grid you need.
Here I have only 2 fixtures, one is a 12x12 rgb grid, and the other is a 10x10 black and white grid.