@ serial killer: what are you aiming at exactly?
your own patch in multiplayer or patches for addons in general (like random numbers...)?
anyway, the patch must be .paa or .pac afaik cos jpgs dont handle transparancy etc.
if you're looking for a way to set custom changeable patches, here's a little tut for you:
1. make a plane in o2, add it to the model and texture it with any of your prospective textures. make it a named selection (e.g. patch1).
2. add your selection name to the cgfmodels section of the config
3. add your selection to the hiddenselection array of your vehicle in the cfgvehicles section. e.g.
hiddenselections[]={"patch1", "patch2"};4. the patches will not appear in game now. they will be 'texturable' via the setobjecttexture command. e.g.
this setobjecttexture [0,"\yourpboname\texture1.paa"] -> would set texture1.pac on the first element in the hiddenselections array
hope that helps...