[D\/8]

Energy does a lot of customization with his ROMs... I recommend using CFC GUI to browse the Manila PNG files to see what file/s are being used for the BG. Form there you can replace those with your own custom, you just have to name them the same.

Edit:
After skimming through the Manila files in EnergyROM Leo, these are the file I found that Make up the BGs.

Portrait:
bg_level0 - 4bfcbbee_manila
bg_level0_bottom - 54612042_manila

Landscape:
bglevel0_landscape_left - 0509ab83_manila
bglevel0_landscape_Right - 47fb5656_manila

I would imagine these would be the files you need to replace. Hope this helps...