As you proly know I am doing a relatively graphically intense project. I just used the image editor to convert the BGs to JPG instead of PNGs. This process did a fairly good job on most of my HD images accept two of the ten looked so-so, and one looked like crap. I decided use PS CS5 to replace the offending JPGs. Now all looks great and all i had to do was upload the revised JPGs.
original BG PNGs 10 x 500kb = 5000kb
construct JPGs 75% 10 x 50kb = 500kb
final:
construct JPGs 75% 7 x 50kb +
my revised jpg's 80% 3 x 120kb = 710kb