Sorry , that we dont help you , but your question is fail.
As first what you mean as BMP Image Buffer? BMP is pseudo for windows bitmap files, that can be coded in tens type of data.
As second when this is place for images, how is your plan to load images to RAM or SDRAM? Normal way is store images in FLASH and you dont need copy it to any RAM, for store, only you copy it to framebuffer to show. And this buffer to show can be RAM or SDRAM.
As third your resolution 1872*1404, when is used for RGB888, need 7,5MB for one image or framebuffer. But you write interface is SPI, then maybe display have own framebuffer internal.
And fifth your internal MCU flash is less as 7,5MB , then i write storing images for this big resolution is possible only on external medium.
Or i can add info , that with use LIBJPEG , you can use this format images in internal flash, and explode it to as you write BMP buffer...in SDRAM
When you plan manage SDRAM in code as arrays and see usage, add region to LD file and use it in code
