2-bit firmware screen flip
Search in your disassembled 6550_2B or 6550_30 firmware for R5:R4=$2000 and right above it you will see R5:R4=$0001. Change the R4 value from $01 to $02 results in your display being configured to scan from Right to Left and from Up to Down which results in the image being flipped upside down. It looks like the blue and green pixels would also have to be swapped in the image you want to display to give true color. You can try the other combinations of those two bits in that byte if you like. This may not be particularly useful, but it does demonstrate the ability to change the LCD parameters.
Search in your disassembled 6550_2B or 6550_30 firmware for R5:R4=$2000 and right above it you will see R5:R4=$0001. Change the R4 value from $01 to $02 results in your display being configured to scan from Right to Left and from Up to Down which results in the image being flipped upside down. It looks like the blue and green pixels would also have to be swapped in the image you want to display to give true color. You can try the other combinations of those two bits in that byte if you like. This may not be particularly useful, but it does demonstrate the ability to change the LCD parameters.