AM625: LVDS integration with custom panel and HMI modification

Hi,
The following are some very general reference documents.
https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/latest/exports/docs/linux/Foundational_Components/Kernel/Kernel_Drivers/Display/DSS7.html 
https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/latest/exports/docs/linux/How_to_Guides/Target/How_to_enable_Microtips_LVDS_Panel.html 
https://www.ti.com/lit/pdf/spradf7 

More specific documentation/support will depend on what you are planning to use:
1) TI EVM or custom board?
2) Which kind of panel does your HMI have? DPI/HDMi or OLDI?

In general, images or GUI are not flashed on a display, rather on the flash on-board with SoC which is driving the display panel.

I have a TI AM62x EVK. I need to interface it with a third-party display that supports LVDS mode. Is it possible to change the background color of the display images? Also, is there any way to change or customize the background images shown on the display?

Like any Image - should display as background image of display.

You may check the plane overlaying feature described on this page: https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/latest/exports/docs/linux/Foundational_Components/Kernel/Kernel_Drivers/Display/DSS7.html#testing-tidss-properties-with-modetest-and-kmstest.

This will help you in overlaying 2 separate streams with adjustable transparency. But if your ask is to modify the existing streams, this will have to be modified in the userspace application driving that stream/pipeline.