Replacing graphics in Car Jamboree

If the question is for me: column number (X/10) * 256 + Y.
If the question is for Aoineko, it seems to be: row number (INT(Y/8)) * 256 + INT(X/8) + (Y MOD 8).

Actually, your tool has way more options than my qucik'n'dirty Bin2Png. If I had known it before, you would have saved me from writing Bin2Png ^_^

car jamboree is a 16K rom, the 32k version is just a reflection of the first bank
to analyze the game sprites you can use MEISEI a MSX1 emulator you can find here
http://www.emu-france.com/emulateurs/10-ordinateurs/167-msx-...
use advanced / sprite viewer
you can see the data of all sprites and search with a hexeditor in the rom

Didn't knew at first. Anyway, it should be like this? right?

Is the openMSX debugger a third party component? I can't seem to find it inside the utilities.

https://github.com/openMSX/debugger/actions for the latest builds (probably only available when logged into GitHub).