Easy thing...
Go to the simfile folder of your song... Example:
Chimera.
Open Chimera.sm file with notepad from there you are going to see something like this:
#TITLE:Chimera;
#SUBTITLE:;
#ARTIST:Yahpp;
#TITLETRANSLIT:;
#SUBTITLETRANSLIT:;
#ARTISTTRANSLIT:;
#CREDIT:;
#BANNER:Banner.png;
#BACKGROUND:Title.png;
#LYRICSPATH:;
#CDTITLE:;
#MUSIC:chimera.mp3;
#OFFSET:0.000;
#SAMPLESTART:85.520;
#SAMPLELENGTH:20.040;
#SELECTABLE:YES;
#BPMS:0.000=210.040;
#STOPS:;
#BGCHANGES:;
You must change where it says "Banner.png" to the complete name of the BGA...
so its gonna says something like this:
#TITLE:Chimera;
#SUBTITLE:;
#ARTIST:Yahpp;
#TITLETRANSLIT:;
#SUBTITLETRANSLIT:;
#ARTISTTRANSLIT:;
#CREDIT:;
#BANNER:Pump It Up NX - Chimera.mpeg;
#BACKGROUND:Title.png;
#LYRICSPATH:;
#CDTITLE:;
#MUSIC:chimera.mp3;
#OFFSET:0.000;
#SAMPLESTART:85.520;
#SAMPLELENGTH:20.040;
#SELECTABLE:YES;
#BPMS:0.000=210.040;
#STOPS:;
#BGCHANGES:;
save the file...
Open Stepmania... then go to the Options and reload all the songs/courses...
and thats it!... you have now a BGA preview!
Mods:
Feel free to move this thread if it doesnt belong here... and to translate better
Credits: Pexx
Translation: Diegomaneira (LOL=P)