I encourage modding!
You will find a lot of older sprites to be simpler than new ones (ex. protagonist vs. shark or kangaroo pooltoys) so I understand people may find older ones subpar, to some degree. Personally I am happy to improve my pixelart over time and to keep older sprites mostly unchanged, so I don't take any offence. I am just happy when people like playing the game.
FYI most character sprites in the game are 48x80 or some multiples of either or both dimensions. Have fun!