"8K RAM could be enough for some animation/graphics."
'328 only has 2K of SRAM,
'2560 has 8K,
'1284 has 16K.
I was thinking if one had 2 arrays, one holding the current picture being displayed, and one holding the next picture being created to display, that would use a lot of data.
However, why bother? The 7219 holds the current picture being displayed - so create it one array, then send it on a regularly scheduled basis, unless one wanted to do some fancy easing from one picture to the next, and also work on the next picture while that was happening. Blink without delay is your friend!