I didn't read everything, but there's a way to use transparent sprites with jpeg, but I don't know if it work ... I write a small code, but I don't try it :
function loadimage(name$,number,filter)
load bitmap name$,1
set current bitmap 1
for x=1 to bitmap width(1)
for y=1 to bitmap height(1)
r = rgbr(point(x,y))
g = rgbg(point(x,y))
b = rgbb(point(x,y))
grey = (r+g+b)/3
if grey < filter then dot x,y,rgb(0,0,0)
next y
next x
get image number,0,0,bitmap width(1),bitmap height(1)
set current bitmap 0
endfunction
here you are ... try with a filter of 10, and try to increase-decrease it

I hope that it work ^_^
"He will come...the voice from the outer world,
bringing the holy war, the Jihad, which will cleanse the Universe and bring us out of darkness."