XPM versus PNG

I was trying to run jfreeciv client yesterday, but it turned out that 
data I have downloaded with win32 client is in png format and jfreeciv 
understands only xpm.

I know that there were some historical reasons, for from 1.3+, java 
itself understands gif,jpg,png and xpm. It is possible to support all 
these 4 formats using same code. How much work would it be to convert 
current loaders to use default java image toolkit ?

Artur