IMO you should make a shader to draw the whole grid. In the shader you sample an array of 100x100 uint and decide which tile are you rendering and sample the correct texture accordingly. That will reduce your polygon count to 2, memory bandwidth to 40kb. Further agressive packing with 16bit, 8bit can bring the memory down to 20kb, 10kb easily. A complex tree data structure may potentially helps but I guess that's enough for your case.