I just trying the change his low res sparks with those Marvel Vs Capcom 2 hitsparks
by Luigi Master.
Well... are you sure the char is using fight.def sparks? If not, it's just a matter of editing the char. Otherwise you can search for a Marvel Vs Capcom screenpack or another hi res screenpack it will have hires sparks. This place
http://mugenguild.com/ has lots of stuff of all kinds, you can try searching there.
If you can't find one you can take the job of making your own Marvel Vs Capcom 2 screenpack.
If you're going to do so, you will have to make everything for fight.def and fight.sff fightfx.sff (which has the fsparks ), including lifebars and everything.
Otherwise you'll get resolution problems since only the sparks will be hi res and everything else will be low res!
In any case you can just edit the char further to make it non fight dependent. you'll add the sparks to the char (I hope the char is also hires or you'll also have trouble.) and change all the sparks related CNS code.
EDIT
Yet before you start wondering "how MUGEN"?
http://www.elecbyte.com/mugendocs/mugen.htmla link to the manual, it has some useful tutorials.
Wait... you say someone else known as Luigi Master already has those sparks? well, in that case I guess you've found a screenpack, you must just install it to your MUGEN just by applying it (I think it has a readme which comes with the instructions... usually it's just a matter of pasting the files in the required folders.)
Hmm... Make sure the screenpack was made for MUGEN 1.0. If that's not the case you may need to add the localcoord parameter and maybe there would be things that won't be... as expected.