Which STM32?
Theoretically, you can use, if in that given model the LTDC has access to FLASH at all, it but it would be impractical. As you cannot overwrite small areas of FLASH without erasing large areas, techniques used to create an image are very limited, and they take long time. Also you cannot display and draw at the same time, so you would need a secondary display source while drawing, or just a blank screen.
JW